print_r

(PHP 4, PHP 5, PHP 7)

print_r — 打印关于变量的易于理解的信息。

描述

bool print_r ( mixed $expression [, bool $return ] )

Note: 参数 return 是在 PHP 4.3.0 的时候加上的

print_r() 显示关于一个变量的易于理解的信息。如果给出的是 string、integer 或 float，将打印变量值本身。如果给出的是 array，将会按照一定格式显示键和元素。object 与数组类似。

记住，print_r() 将把数组的指针移到最后边。使用 reset() 可让指针回到开始处。

<pre>
<?php
    $a = array ('a' => 'apple', 'b' => 'banana', 'c' => array ('x','y','z'));
    print_r ($a);
?>
</pre>

上边的代码将输出： 

<pre>
Array
(
    [a] => apple
    [b] => banana
    [c] => Array
        (
            [0] => x
            [1] => y
            [2] => z
        )
)
</pre>

如果想捕捉 print_r() 的输出，可使用 return 参数。若此参数设为 TRUE，print_r() 将不打印结果（此为默认动作），而是返回其输出。

Example #1 return 参数示例

<?php
    $b = array ('m' => 'monkey', 'foo' => 'bar', 'x' => array ('x', 'y', 'z'));
    $results = print_r ($b, true); //$results 包含了 print_r 的输出结果
?>

Note: 如果想在 PHP 4.3.0 之前的版本中捕捉 print_r() 的输出，可使用输出控制函数。

Note: 在 PHP 4.0.4 之前的版本中，如果给出的 array 或 object 包含了直接或间接指向自身的引用，print_r() 将永远继续下去。print_r($GLOBALS) 就是一个例子，因为 $GLOBALS 自身即是全局变量，其包含了指向自身的引用。

参见 ob_start()、var_dump() 和 var_export()。

User Contributed Notes

Soaku 29-Sep-2017 01:47
liamtoh6@hotmail.com posted a function that will echo print_r output with proper new lines in HTML files. He used <pre> for it to work, but that might not be always the best method to go. For example, it is not valid to place <pre> inside <p>.

Here is my way to do this:

<?php

function print_rbr ($var, $return = false) {
  $r = nl2br(htmlspecialchars(print_r($var, true)));
  if ($return) return $r;
  else echo $r;
}

?>

This function will:

- Place <br> where newlines are,
- Escape unsecure characters with HTML entities.
Soaku 28-Jul-2017 07:24
Remember to always htmlspecialchars print_r output, if it can contain html characters.

<?php

$array = array("<some>html<tags>");

print_r($array); // Invalid output, HTML breaks.
echo htmlspecialchars(print_r($array, true)); // Works and doesn't break the output.
?>
simivar at gmail dot com 21-Jun-2017 10:31
I've fixed function wrote by Matt to reverse print_r - it had problems with null values. Created a GIST for that too so please add any future fixes in there instead of this comment section:
https://gist.github.com/simivar/037b13a9bbd53ae5a092d8f6d9828bc3

<?php
/**
  * Matt: core
  * Trixor: object handling
  * lech: Windows suppport
  * simivar: null support
  *
  * @see http://php.net/manual/en/function.print-r.php
  **/
function print_r_reverse($input) {
        $lines = preg_split('#\r?\n#', trim($input));
        if (trim($lines[ 0 ]) != 'Array' && trim($lines[ 0 ] != 'stdClass Object')) {
            // bottomed out to something that isn't an array or object
            if ($input === '') {
                return null;
            }
           
            return $input;
        } else {
            // this is an array or object, lets parse it
            $match = array();
            if (preg_match("/(\s{5,})\(/", $lines[ 1 ], $match)) {
                // this is a tested array/recursive call to this function
                // take a set of spaces off the beginning
                $spaces = $match[ 1 ];
                $spaces_length = strlen($spaces);
                $lines_total = count($lines);
                for ($i = 0; $i < $lines_total; $i++) {
                    if (substr($lines[ $i ], 0, $spaces_length) == $spaces) {
                        $lines[ $i ] = substr($lines[ $i ], $spaces_length);
                    }
                }
            }
            $is_object = trim($lines[ 0 ]) == 'stdClass Object';
            array_shift($lines); // Array
            array_shift($lines); // (
            array_pop($lines); // )
            $input = implode("\n", $lines);
            $matches = array();
            // make sure we only match stuff with 4 preceding spaces (stuff for this array and not a nested one)
            preg_match_all("/^\s{4}\[(.+?)\] \=\> /m", $input, $matches, PREG_OFFSET_CAPTURE | PREG_SET_ORDER);
            $pos = array();
            $previous_key = '';
            $in_length = strlen($input);
            // store the following in $pos:
            // array with key = key of the parsed array's item
            // value = array(start position in $in, $end position in $in)
            foreach ($matches as $match) {
                $key = $match[ 1 ][ 0 ];
                $start = $match[ 0 ][ 1 ] + strlen($match[ 0 ][ 0 ]);
                $pos[ $key ] = array($start, $in_length);
                if ($previous_key != '') {
                    $pos[ $previous_key ][ 1 ] = $match[ 0 ][ 1 ] - 1;
                }
                $previous_key = $key;
            }
            $ret = array();
            foreach ($pos as $key => $where) {
                // recursively see if the parsed out value is an array too
                $ret[ $key ] = print_r_reverse(substr($input, $where[ 0 ], $where[ 1 ] - $where[ 0 ]));
            }
           
            return $is_object ? (object)$ret : $ret;
        }
    }
?>
anymix dot services at gmail dot com 28-May-2017 01:31
// New var export option

function varExp($E,$vE){
    $vE.="=array(";$sep="";
    foreach ($E as $veK => $veV) {
        $vE.=$sep."'$veK'=>'$veV'";$sep=",";
    }
    $vE.=");";
    return $vE;
}

print varExp($I,"\$I");
lech 03-May-2017 05:30
A slight amendment to Matt's awesome print_r_reverse function (Thank You, a life-saver - data recovery :-) . If the output is copied from a Windows system, the end of lines may include the return character "\r" and so the scalar (string) elements will include a trailing "\r" character that isn't suppose to be there. To resolve, replace the first line in the function with...

<?php $lines = preg_split('#\r?\n#', trim($in)); ?>

This will work for both cases (Linux and Windows).

I include the entire function below for completeness, but all credit to Matt, the original author, Thank You.

<?php
//Author: Matt (http://us3.php.net/print_r)
function print_r_reverse($in) {
    $lines = preg_split('#\r?\n#', trim($in));
    if (trim($lines[0]) != 'Array') {
        // bottomed out to something that isn't an array
        return $in;
    } else {
        // this is an array, lets parse it
        if (preg_match("/(\s{5,})\(/", $lines[1], $match)) {
            // this is a tested array/recursive call to this function
            // take a set of spaces off the beginning
            $spaces = $match[1];
            $spaces_length = strlen($spaces);
            $lines_total = count($lines);
            for ($i = 0; $i < $lines_total; $i++) {
                if (substr($lines[$i], 0, $spaces_length) == $spaces) {
                    $lines[$i] = substr($lines[$i], $spaces_length);
                }
            }
        }
        array_shift($lines); // Array
        array_shift($lines); // (
        array_pop($lines); // )
        $in = implode("\n", $lines);
        // make sure we only match stuff with 4 preceding spaces (stuff for this array and not a nested one)
        preg_match_all("/^\s{4}\[(.+?)\] \=\> /m", $in, $matches, PREG_OFFSET_CAPTURE | PREG_SET_ORDER);
        $pos = array();
        $previous_key = '';
        $in_length = strlen($in);
        // store the following in $pos:
        // array with key = key of the parsed array's item
        // value = array(start position in $in, $end position in $in)
        foreach ($matches as $match) {
            $key = $match[1][0];
            $start = $match[0][1] + strlen($match[0][0]);
            $pos[$key] = array($start, $in_length);
            if ($previous_key != '') $pos[$previous_key][1] = $match[0][1] - 1;
            $previous_key = $key;
        }
        $ret = array();
        foreach ($pos as $key => $where) {
            // recursively see if the parsed out value is an array too
            $ret[$key] = print_r_reverse(substr($in, $where[0], $where[1] - $where[0]));
        }
        return $ret;
    }
}
?>
Trixor 02-Feb-2017 04:12
I've made a small improvement to the print_r_reverse function to also handle objects. Thanks to Matt for making the original.

<?php
function print_r_reverse($in) {
  $lines = explode("\n", trim($in));
  if (trim($lines[0]) != 'Array' && trim($lines[0] != 'stdClass Object')) {
// bottomed out to something that isn't an array or object
    return $in;
  } else {
// this is an array or object, lets parse it
    $match = array();
    if (preg_match("/(\s{5,})\(/", $lines[1], $match)) {
// this is a tested array/recursive call to this function
// take a set of spaces off the beginning
      $spaces = $match[1];
      $spaces_length = strlen($spaces);
      $lines_total = count($lines);
      for ($i = 0; $i < $lines_total; $i++) {
        if (substr($lines[$i], 0, $spaces_length) == $spaces) {
          $lines[$i] = substr($lines[$i], $spaces_length);
        }
      }
    }
    $is_object = trim($lines[0]) == 'stdClass Object';
    array_shift($lines); // Array
    array_shift($lines); // (
    array_pop($lines); // )
    $in = implode("\n", $lines);
    $matches = array();
// make sure we only match stuff with 4 preceding spaces (stuff for this array and not a nested one)
    preg_match_all("/^\s{4}\[(.+?)\] \=\> /m", $in, $matches, PREG_OFFSET_CAPTURE | PREG_SET_ORDER);
    $pos = array();
    $previous_key = '';
    $in_length = strlen($in);
// store the following in $pos:
// array with key = key of the parsed array's item
// value = array(start position in $in, $end position in $in)
    foreach ($matches as $match) {
      $key = $match[1][0];
      $start = $match[0][1] + strlen($match[0][0]);
      $pos[$key] = array($start, $in_length);
      if ($previous_key != '') {
        $pos[$previous_key][1] = $match[0][1] - 1;
      }
      $previous_key = $key;
    }
    $ret = array();
    foreach ($pos as $key => $where) {
// recursively see if the parsed out value is an array too
      $ret[$key] = print_r_reverse(substr($in, $where[0], $where[1] - $where[0]));
    }
    return $is_object ? (object) $ret : $ret;
  }
}
?>
ntd at entidi dot it 01-Aug-2015 02:43
Another attempt that tries to overcome the memory blowout when the passed in data has mutual recursion.

<?php
function safe_print_r($data, $nesting = 5, $indent = '') {
    if (! is_object($data) && ! is_array($data)) {
        var_dump($data);
    } elseif ($nesting < 0) {
        echo "** MORE **\n";
    } else {
        echo ucfirst(gettype($data)) . " (\n";
        foreach ((array) $data as $k => $v) {
            echo $indent . "\t[$k] => ";
            safe_print_r($v, $nesting - 1, "$indent\t");
        }
        echo "$indent)\n";
    }
}
?>
Sumit 27-May-2015 10:20
I prefer to use
<?php
printf("<pre>%s</pre>",print_r($_POST, true));
?>
Simon Asika 07-Nov-2013 01:06
Here is a print_r() clone but support max level limit.

When we want to print a big object, this will help us get a clean dumping data.

<?php

/**
 * Recrusive print variables and limit by level.
 *
 * @param   mixed  $data   The variable you want to dump.
 * @param   int    $level  The level number to limit recrusive loop.
 *
 * @return  string  Dumped data.
 *
 * @author  Simon Asika (asika32764[at]gmail com)
 * @date    2013-11-06
 */
function print_r_level($data, $level = 5)
{
    static $innerLevel = 1;
   
    static $tabLevel = 1;
   
    static $cache = array();
   
    $self = __FUNCTION__;
   
    $type       = gettype($data);
    $tabs       = str_repeat('    ', $tabLevel);
    $quoteTabes = str_repeat('    ', $tabLevel - 1);
   
    $recrusiveType = array('object', 'array');
   
    // Recrusive
    if (in_array($type, $recrusiveType))
    {
        // If type is object, try to get properties by Reflection.
        if ($type == 'object')
        {
            if (in_array($data, $cache))
            {
                return "\n{$quoteTabes}*RECURSION*\n";
            }
           
            // Cache the data
            $cache[] = $data;
           
            $output     = get_class($data) . ' ' . ucfirst($type);
            $ref        = new \ReflectionObject($data);
            $properties = $ref->getProperties();
           
            $elements = array();
           
            foreach ($properties as $property)
            {
                $property->setAccessible(true);
               
                $pType = $property->getName();
               
                if ($property->isProtected())
                {
                    $pType .= ":protected";
                }
                elseif ($property->isPrivate())
                {
                    $pType .= ":" . $property->class . ":private";
                }
               
                if ($property->isStatic())
                {
                    $pType .= ":static";
                }
               
                $elements[$pType] = $property->getValue($data);
            }
        }
        // If type is array, just retun it's value.
        elseif ($type == 'array')
        {
            $output = ucfirst($type);
            $elements = $data;
        }
       
        // Start dumping datas
        if ($level == 0 || $innerLevel < $level)
        {
            // Start recrusive print
            $output .= "\n{$quoteTabes}(";
           
            foreach ($elements as $key => $element)
            {
                $output .= "\n{$tabs}[{$key}] => ";
               
                // Increment level
                $tabLevel = $tabLevel + 2;
                $innerLevel++;
               
                $output  .= in_array(gettype($element), $recrusiveType) ? $self($element, $level) : $element;
               
                // Decrement level
                $tabLevel = $tabLevel - 2;
                $innerLevel--;
            }
           
            $output .= "\n{$quoteTabes})\n";
        }
        else
        {
            $output .= "\n{$quoteTabes}*MAX LEVEL*\n";
        }
    }
   
    // Clean cache
    if($innerLevel == 1)
    {
        $cache = array();
    }
   
    return $output;
}// End function

// TEST ------------------------------------

class testClass
{
    protected $a = 'aaa';
   
    private $b = 'bbb';
   
    public $c = array(1, 2, ['a', 'b', 'c'], 4);
   
    static public $d = 'ddd';
   
    static protected $e = 'eee';
}

$test = new testClass;

$test->testClass = $test;

echo '<pre>' . print_r_level($test, 3) . '</pre>';

?>

will output
-------------------------------------------------------------

testClass Object
(
    [a:protected] => aaa
    [b:testClass:private] => bbb
    [c] => Array
        (
            [0] => 1
            [1] => 2
            [2] => Array
                *MAX LEVEL*

            [3] => 4
        )

    [d:static] => ddd
    [e:protected:static] => eee
    [testClass] =>
        *RECURSION*

)
preda dot vlad at yahoo dot com 22-Mar-2013 06:40
print_r(), just like var_dump() does NOT cast an object, not even if it has a __toString() method - which is normal.

<?php
class A {
    public function __toString() {
        return 'In class A';
    }
}
$a = new A;
echo $a; // In class A
print_r($a); // A Object()
// you can simulate the echo by casting it manually
print_r((string)$a);  // In class A
henzeberkheij at gmail dot com 29-Jan-2012 12:10
print_r is used for debug purposes. Yet I had some classes where I just wanted the values coming out of the database, not all the other crap. thus i wrote the following function. If your class has an toArray function, that one will be called otherwise it will return the object as is. print_neat_classes_r is the function that should be called!

<?php
print_neat_classes_r($array, $return=false){
        return print_r(self::neat_class_print_r($array), $return);
    }
   
function do_print_r($array, $return=false){
        if(is_object($array) && method_exists($array, 'toArray')){
            return $array->toArray();
        }else if(is_array($array)){
            foreach($array as $key=>$obj){
                $array[$key] = self::do_print_r($obj, $return);
            }
            return $array;
        }else{
            return $array;
        }
    }
?>
eithed 21-Oct-2011 11:25
Bear in mind that print_r actually reserves some memory to do something - so, for example thing like:

<?php
function shutdown_handler()
{
    file_put_contents($_SERVER['DOCUMENT_ROOT']."/log.txt", print_r($_REQUEST, true));
}

ini_set('memory_limit', '1M');
register_shutdown_function("shutdown_handler");

$array = array();
while(true)
    $array[] = new stdClass();
?>

will just not work. Try using var_export, and presto, everything is fine.
machuidel 03-Feb-2011 01:01
The following will output an array in a PHP parsable format:

<?php
function serialize_array(&$array, $root = '$root', $depth = 0)
{
        $items = array();

        foreach($array as $key => &$value)
        {
                if(is_array($value))
                {
                        serialize_array($value, $root . '[\'' . $key . '\']', $depth + 1);
                }
                else
                {
                        $items[$key] = $value;
                }
        }

        if(count($items) > 0)
        {
                echo $root . ' = array(';

                $prefix = '';
                foreach($items as $key => &$value)
                {
                        echo $prefix . '\'' . $key . '\' => \'' . addslashes($value) . '\'';
                        $prefix = ', ';
                }

                echo ');' . "\n";
        }
}
?>
Alexander 19-Mar-2010 02:20
A simple function to send the output of print_r to firebug.
The script creates a dummy console object with a log method for when firebug is disabled/not available.

<?php
function debug ($data) {
    echo "<script>\r\n//<![CDATA[\r\nif(!console){var console={log:function(){}}}";
    $output    =    explode("\n", print_r($data, true));
    foreach ($output as $line) {
        if (trim($line)) {
            $line    =    addslashes($line);
            echo "console.log(\"{$line}\");";
        }
    }
    echo "\r\n//]]>\r\n</script>";
}
?>
liamtoh6 at hotmail dot com 03-Feb-2010 07:01
I add this function to the global scope on just about every project I do, it makes reading the output of print_r() in a browser infinitely easier.

<?php
function print_r2($val){
        echo '<pre>';
        print_r($val);
        echo  '</pre>';
}
?>

It also makes sense in some cases to add an if statement to only display the output in certain scenarios, such as:

if(debug==true)
if($_SERVER['REMOTE_ADDR'] == '127.0.0.1')
Matt 14-Sep-2009 09:53
Here is another version that parses the print_r() output. I tried the one posted, but I had difficulties with it. I believe it has a problem with nested arrays. This handles nested arrays without issue as far as I can tell.

<?php
function print_r_reverse($in) {
    $lines = explode("\n", trim($in));
    if (trim($lines[0]) != 'Array') {
        // bottomed out to something that isn't an array
        return $in;
    } else {
        // this is an array, lets parse it
        if (preg_match("/(\s{5,})\(/", $lines[1], $match)) {
            // this is a tested array/recursive call to this function
            // take a set of spaces off the beginning
            $spaces = $match[1];
            $spaces_length = strlen($spaces);
            $lines_total = count($lines);
            for ($i = 0; $i < $lines_total; $i++) {
                if (substr($lines[$i], 0, $spaces_length) == $spaces) {
                    $lines[$i] = substr($lines[$i], $spaces_length);
                }
            }
        }
        array_shift($lines); // Array
        array_shift($lines); // (
        array_pop($lines); // )
        $in = implode("\n", $lines);
        // make sure we only match stuff with 4 preceding spaces (stuff for this array and not a nested one)
        preg_match_all("/^\s{4}\[(.+?)\] \=\> /m", $in, $matches, PREG_OFFSET_CAPTURE | PREG_SET_ORDER);
        $pos = array();
        $previous_key = '';
        $in_length = strlen($in);
        // store the following in $pos:
        // array with key = key of the parsed array's item
        // value = array(start position in $in, $end position in $in)
        foreach ($matches as $match) {
            $key = $match[1][0];
            $start = $match[0][1] + strlen($match[0][0]);
            $pos[$key] = array($start, $in_length);
            if ($previous_key != '') $pos[$previous_key][1] = $match[0][1] - 1;
            $previous_key = $key;
        }
        $ret = array();
        foreach ($pos as $key => $where) {
            // recursively see if the parsed out value is an array too
            $ret[$key] = print_r_reverse(substr($in, $where[0], $where[1] - $where[0]));
        }
        return $ret;
    }
}

?>
Bob 08-May-2009 12:19
Here is a function that formats the output of print_r as a expandable/collapsable tree list using HTML and JavaScript.
<?php
function print_r_tree($data)
{
    // capture the output of print_r
    $out = print_r($data, true);

    // replace something like '[element] => <newline> (' with <a href="javascript:toggleDisplay('...');">...</a><div id="..." style="display: none;">
    $out = preg_replace('/([ \t]*)(\[[^\]]+\][ \t]*\=\>[ \t]*[a-z0-9 \t_]+)\n[ \t]*\(/iUe',"'\\1<a href=\"javascript:toggleDisplay(\''.(\$id = substr(md5(rand().'\\0'), 0, 7)).'\');\">\\2</a><div id=\"'.\$id.'\" style=\"display: none;\">'", $out);

    // replace ')' on its own on a new line (surrounded by whitespace is ok) with '</div>
    $out = preg_replace('/^\s*\)\s*$/m', '</div>', $out);

    // print the javascript function toggleDisplay() and then the transformed output
    echo '<script language="Javascript">function toggleDisplay(id) { document.getElementById(id).style.display = (document.getElementById(id).style.display == "block") ? "none" : "block"; }</script>'."\n$out";
}
?>
Pass it a multidimensional array or object and each sub-array/object will be hidden and replaced by a html link that will toggle its display on and off.
Its quick and dirty, but great for debugging the contents of large arrays and objects.
Note: You'll want to surround the output with <pre></pre>
sebasg37 at gmail dot com 26-Jan-2009 06:35
If you have to catch the output without showing it at all at first (for example, if you want to append the print_r output to a file), you can do this:

<?php

ob_start();
print_r( $some_array );
$output = ob_get_clean();

// if you want to append the print_r output of $some_array to, let's say, log.txt:

file_put_contents( 'log.txt', file_get_contents( 'log.txt' ) . $output )

?>
afisher8 at cox dot net 17-Dec-2008 05:53
I use this all the time when debugging objects, but when you have a very large object with big arrays of sub-objects, it's easy to get overwhelmed with the large amount of output....sometimes you don't want to see absolutely every sub-object.

I made this function to debug objects while "hiding" sub-objects of certain types.  This also color codes the output for a more readable printout.

<?php

function wtf($var, $arrayOfObjectsToHide=null, $fontSize=11)
{
    $text = print_r($var, true);

    if (is_array($arrayOfObjectsToHide)) {
   
        foreach ($arrayOfObjectsToHide as $objectName) {
   
            $searchPattern = '#('.$objectName.' Object\n(\s+)\().*?\n\2\)\n#s';
            $replace = "$1<span style=\"color: #FF9900;\">--&gt; HIDDEN - courtesy of wtf() &lt;--</span>)";
            $text = preg_replace($searchPattern, $replace, $text);
        }
    }

    // color code objects
    $text = preg_replace('#(\w+)(\s+Object\s+\()#s', '<span style="color: #079700;">$1</span>$2', $text);
    // color code object properties
    $text = preg_replace('#\[(\w+)\:(public|private|protected)\]#', '[<span style="color: #000099;">$1</span>:<span style="color: #009999;">$2</span>]', $text);
   
    echo '<pre style="font-size: '.$fontSize.'px; line-height: '.$fontSize.'px;">'.$text.'</pre>';
}

// example usage:
wtf($myBigObject, array('NameOfObjectToHide_1', 'NameOfObjectToHide_2'));

?>
kurt krueckeberg 28-Oct-2008 07:53
This is an alternative for printing arrays. It bolds array values.

<?php
function print_array(&$a, $str = "")
{
    if ($str[0]) {
        echo "$str =";
    }
    echo ' array( ';
    foreach ($a as $k => $v) {

        echo "[$k]".' => ';

        if (is_array($v)) {
            print_array($v);
        }
        else {   
               echo "<strong>$a[$k]</strong> ";
        }
    }
    echo ')  ';
}
$a1 = array ("apples", "oranges", "pears");
$a2 = array ("potatos", "green beans", "squash");
$a3 = array ("euros", "dollars", "pesos", "dinars");
$test = range(1, 9);
array_push($test, array ("fruit" => $a1, "vegies" => $a2, "money" => $a3));
print_array($test, "test");
?>
schizo do not spamme duckie at gmail dot com 07-Oct-2008 02:00
my take on the highlighted markupped debug function:

<?php
/**
 * print_array()
 * Does a var_export of the array and returns it between <pre> tags
 *
 * @param mixed $var any input you can think of
 * @return string HTML
 */
function print_array($var)
{
    $input =var_export($var,true);
    $input = preg_replace("! => \n\W+ array \(!Uims", " => Array ( ", $input);
    $input = preg_replace("!array \(\W+\),!Uims", "Array ( ),", $input);
    return("<pre>".str_replace('><?', '>', highlight_string('<'.'?'.$input, true))."</pre>");
}
?>
brenden at beagleproductions dot com 28-Aug-2008 10:58
Many developers have submitted bugs to the PHP development team with regards to print_r showing protected and private properties of objects (PHP 5).  This is not a bug; sensitive information (ex. database connection object) should be  encapsulated within a private member function of your class.
admin at swivelgames dot com 17-Aug-2008 10:44
I was having problems using print_r because I didn't like the fact that if tags where included in the array it would still be parsed by the browsers.

Heres a simple fix for anyone who is having the same problem as I did. This will output your text properly for viewing through the browser instead of the browser's "view source" or CLI.

Script:
<?php

     $MyArray[0]="<div align='center'>My Text</div>";

     echo "<pre>".htmlspecialchars(print_r($MyArray,true))."</pre>";

?>

Output:
<pre>Array
(
    [0] =&gt; &lt;div align='center'&gt;My Text&lt;/div&gt;
)
</pre>
Anonymous 28-Jun-2008 10:21
I have written a nice debugging function.
This function handles arrays beautifully.
<?php
//Debug variables, $i and $k are for recursive use
function DebugDisplayVar($input, $name = "Debug", $i = "0", $k = array("Error")){
    if(is_array($input))
    {    foreach ($input as $i => $value){
            $temp = $k;
            $temp[] = $i;
            DebugDisplayVar($value, $name, $i, $temp);}
    }else{//if not array
        echo "$".$name;//[$k]
        foreach ($k as $i => $value){
            if($value !=="Error"){echo "[$value]";}
        }
        echo " = $input<br>";
}    }

//outputs
Debug[0] = value
Debug[1] = another value
ect...

?>
janci 13-May-2008 11:49
You cannot use print_r(), var_dump() nor var_export() to get static member variables of a class. However, in PHP5 you can use Reflection classes for this:

<?php

$reflection = new ReflectionClass('Static');
print_r($reflection->getStaticProperties());

?>
helpful at maybe dot com 07-Mar-2008 05:13
Another slight modification to the previous post to allow for empty array elements

added the following lines after the first preg_match block
<?php
        } else if ($expecting == 2 && preg_match('/^\[(.+?)\] \=\>$/', $trim, $matches)) { // array element
            // the array element is blank
            list ($fullMatch, $key) = $matches;
            $topArray[$key] = $element;
        }

?>
anon at anon dot com 29-Feb-2008 07:30
A slight modification to the previous post to allow for arrays containing mutli line strings. haven't fully tested it with everything, but seems to work great for the stuff i've done so far.

<?php

function print_r_reverse(&$output)
{
    $expecting = 0; // 0=nothing in particular, 1=array open paren '(', 2=array element or close paren ')'
    $lines = explode("\n", $output);
    $result = null;
    $topArray = null;
    $arrayStack = array();
    $matches = null;
    while (!empty($lines) && $result === null)
    {
        $line = array_shift($lines);
        $trim = trim($line);
        if ($trim == 'Array')
        {
            if ($expecting == 0)
            {
                $topArray = array();
                $expecting = 1;
            }
            else
            {
                trigger_error("Unknown array.");
            }
        }
        else if ($expecting == 1 && $trim == '(')
        {
            $expecting = 2;
        }
        else if ($expecting == 2 && preg_match('/^\[(.+?)\] \=\> (.+)$/', $trim, $matches)) // array element
        {
            list ($fullMatch, $key, $element) = $matches;
            if (trim($element) == 'Array')
            {
                $topArray[$key] = array();
                $newTopArray =& $topArray[$key];
                $arrayStack[] =& $topArray;
                $topArray =& $newTopArray;
                $expecting = 1;
            }
            else
            {
                $topArray[$key] = $element;
            }
        }
        else if ($expecting == 2 && $trim == ')') // end current array
        {
            if (empty($arrayStack))
            {
                $result = $topArray;
            }
            else // pop into parent array
            {
                // safe array pop
                $keys = array_keys($arrayStack);
                $lastKey = array_pop($keys);
                $temp =& $arrayStack[$lastKey];
                unset($arrayStack[$lastKey]);
                $topArray =& $temp;
            }
        }
        // Added this to allow for multi line strings.
    else if (!empty($trim) && $expecting == 2)
    {
        // Expecting close parent or element, but got just a string
        $topArray[$key] .= "\n".$line;
    }
        else if (!empty($trim))
        {
            $result = $line;
        }
    }
  
    $output = implode(n, $lines);
    return $result;
}

/**
 * @param string $output : The output of a multiple print_r calls, separated by newlines
 * @return mixed[] : parseable elements of $output
 */
function print_r_reverse_multiple($output)
{
    $result = array();
    while (($reverse = print_r_reverse($output)) !== NULL)
    {
        $result[] = $reverse;
    }
    return $result;
}

$output = '
Array
(
    [a] => apple
    [b] => banana
    [c] => Array
        (
            [0] => x
            [1] => y
            [2] => z
            [3] => Array
            (
                [nest] => yes
                [nest2] => Array
                (
                    [nest] => some more
                    asffjaskkd
                )
                [nest3] => o rly?
            )
        )
)

some extra stuff
';
var_dump(print_r_reverse($output), $output);

?>

This should output

array(3) {
  ["a"]=>
  string(5) "apple"
  ["b"]=>
  string(6) "banana"
  ["c"]=>
  array(4) {
    [0]=>
    string(1) "x"
    [1]=>
    string(1) "y"
    [2]=>
    string(1) "z"
    [3]=>
    array(3) {
      ["nest"]=>
      string(3) "yes"
      ["nest2"]=>
      array(1) {
        ["nest"]=>
        string(40) "some more
                    asffjaskkd"
      }
      ["nest3"]=>
      string(6) "o rly?"
    }
  }
}
string(18) "nsome extra stuffn"

Added:
else if (!empty($trim) && $expecting == 2)
{
    // Expecting close parent or element, but got just a string
    $topArray[$key] .= "\n".$line;
}
bart at mediawave dot nl 31-Oct-2007 01:27
Here's a PHP version of print_r which can be tailored to your needs. Shows protected and private properties of objects and detects recursion (for objects only!). Usage:

void u_print_r ( mixed $expression [, array $ignore] )

Use the $ignore parameter to provide an array of property names that shouldn't be followed recursively.

<?php

function u_print_r($subject, $ignore = array(), $depth = 1, $refChain = array())
{
    if ($depth > 20) return;
    if (is_object($subject)) {
        foreach ($refChain as $refVal)
            if ($refVal === $subject) {
                echo "*RECURSION*\n";
                return;
            }
        array_push($refChain, $subject);
        echo get_class($subject) . " Object ( \n";
        $subject = (array) $subject;
        foreach ($subject as $key => $val)
            if (is_array($ignore) && !in_array($key, $ignore, 1)) {
                echo str_repeat(" ", $depth * 4) . '[';
                if ($key{0} == "\0") {
                    $keyParts = explode("\0", $key);
                    echo $keyParts[2] . (($keyParts[1] == '*')  ? ':protected' : ':private');
                } else
                    echo $key;
                echo '] => ';
                u_print_r($val, $ignore, $depth + 1, $refChain);
            }
        echo str_repeat(" ", ($depth - 1) * 4) . ")\n";
        array_pop($refChain);
    } elseif (is_array($subject)) {
        echo "Array ( \n";
        foreach ($subject as $key => $val)
            if (is_array($ignore) && !in_array($key, $ignore, 1)) {
                echo str_repeat(" ", $depth * 4) . '[' . $key . '] => ';
                u_print_r($val, $ignore, $depth + 1, $refChain);
            }
        echo str_repeat(" ", ($depth - 1) * 4) . ")\n";
    } else
        echo $subject . "\n";
}

?>

Example:

<?php

class test {

    public $var1 = 'a';
    protected $var2 = 'b';
    private $var3 = 'c';
    protected $array = array('x', 'y', 'z');

}

$test = new test();
$test->recursiveRef = $test;
$test->anotherRecursiveRef->recursiveRef = $test;
$test->dont->follow = 'me';

u_print_r($test, array('dont'));

?>

Will produce:

test Object (
    [var1] => a
    [var2:protected] => b
    [var3:private] => c
    [array:protected] => Array (
        [0] => x
        [1] => y
        [2] => z
    )
    [recursiveRef] => *RECURSION*
    [anotherRecursiveRef] => stdClass Object (
        [recursiveRef] => *RECURSION*
    )
)
motin at demomusic dot nu 20-Jun-2007 01:01
This works around the hacky nature of print_r in return mode (using output buffering for the return mode to work is hacky...):

<?php
/**
  * An alternative to print_r that unlike the original does not use output buffering with
  * the return parameter set to true. Thus, Fatal errors that would be the result of print_r
  * in return-mode within ob handlers can be avoided.
  *
  * Comes with an extra parameter to be able to generate html code. If you need a
  * human readable DHTML-based print_r alternative, see http://krumo.sourceforge.net/
  *
  * Support for printing of objects as well as the $return parameter functionality
  * added by Fredrik Wollsén (fredrik dot motin at gmail), to make it work as a drop-in
  * replacement for print_r (Except for that this function does not output
  * paranthesises around element groups... ;) )
  *
  * Based on return_array() By Matthew Ruivo (mruivo at gmail)
  * (http://se2.php.net/manual/en/function.print-r.php#73436)
  */
function obsafe_print_r($var, $return = false, $html = false, $level = 0) {
    $spaces = "";
    $space = $html ? "&nbsp;" : " ";
    $newline = $html ? "<br />" : "\n";
    for ($i = 1; $i <= 6; $i++) {
        $spaces .= $space;
    }
    $tabs = $spaces;
    for ($i = 1; $i <= $level; $i++) {
        $tabs .= $spaces;
    }
    if (is_array($var)) {
        $title = "Array";
    } elseif (is_object($var)) {
        $title = get_class($var)." Object";
    }
    $output = $title . $newline . $newline;
    foreach($var as $key => $value) {
        if (is_array($value) || is_object($value)) {
            $level++;
            $value = obsafe_print_r($value, true, $html, $level);
            $level--;
        }
        $output .= $tabs . "[" . $key . "] => " . $value . $newline;
    }
    if ($return) return $output;
      else echo $output;
}
?>

Built on a function earlier posted in these comments as stated in the Doc comment. Cheers! /Fredrik (Motin)
Enthusiastic PHPers 22-Mar-2007 09:03
We had an interesting problem dumping an object that
contained embedded HTML. The application makes use
of buffer manipulation functions, so print_r's 2nd argument
wasn't helpful. Here is how we solved the problem:

$object = new ObjectContainingHTML();
$savedbuffercontents = ob_get_clean();
print_r($object);
$print_r_output = ob_get_clean();
ob_start();
echo $savedbuffercontents;
echo htmlentities($print_r_output);
Matthew Ruivo (mruivo at gmail) 23-Feb-2007 07:47
For those of you needing to print an array within a buffer callback function, I've created this quick function. It simply returns the array as a readable string rather than printing it. You can even choose whether to return it in normal text-mode or HTML. It's recursive, so multi-dimensial arrays are supported. I hope someone finds this useful!

<?php

    function return_array($array, $html = false, $level = 0) {
        $space = $html ? "&nbsp;" : " ";
        $newline = $html ? "<br />" : "\n";
        for ($i = 1; $i <= 6; $i++) {
            $spaces .= $space;
        }
        $tabs = $spaces;
        for ($i = 1; $i <= $level; $i++) {
            $tabs .= $spaces;
        }
        $output = "Array" . $newline . $newline;
        foreach($array as $key => $value) {
            if (is_array($value)) {
                $level++;
                $value = return_array($value, $html, $level);
                $level--;
            }
            $output .= $tabs . "[" . $key . "] => " . $value . $newline;
        }
        return $output;
    }

?>
reinder at fake-address dot com 31-Jan-2006 06:09
I always use this function in my code, because most of my functions return an Array or Boolean :

<?php

function printr ( $object , $name = '' ) {

    print ( '\'' . $name . '\' : ' ) ;

    if ( is_array ( $object ) ) {
        print ( '<pre>' )  ;
        print_r ( $object ) ;
        print ( '</pre>' ) ;
    } else {
        var_dump ( $object ) ;
    }

}

?>

( print_r gives no output on FALSE and that can be annoying! )
thbley at gmail dot com 16-Nov-2005 09:10
Here is a print_r that produces xml:
(now you can expand/collapse the nodes in your browser)

<?php
header('Content-Type: text/xml; CHARSET=gb2312');
echo print_r_xml($some_var);

function print_r_xml($arr,$first=true) {
  $output = "";
  if ($first) $output .= "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n<data>\n";
  foreach($arr as $key => $val) {
    if (is_numeric($key)) $key = "arr_".$key; // <0 is not allowed
    switch (gettype($val)) {
      case "array":
        $output .= "<".htmlspecialchars($key)." type='array' size='".count($val)."'>".
          print_r_xml($val,false)."</".htmlspecialchars($key).">\n"; break;
      case "boolean":
        $output .= "<".htmlspecialchars($key)." type='bool'>".($val?"true":"false").
          "</".htmlspecialchars($key).">\n"; break;
      case "integer":
        $output .= "<".htmlspecialchars($key)." type='integer'>".
          htmlspecialchars($val)."</".htmlspecialchars($key).">\n"; break;
      case "double":
        $output .= "<".htmlspecialchars($key)." type='double'>".
          htmlspecialchars($val)."</".htmlspecialchars($key).">\n"; break;
      case "string":
        $output .= "<".htmlspecialchars($key)." type='string' size='".strlen($val)."'>".
          htmlspecialchars($val)."</".htmlspecialchars($key).">\n"; break;
      default:
        $output .= "<".htmlspecialchars($key)." type='unknown'>".gettype($val).
          "</".htmlspecialchars($key).">\n"; break;
    }
  }
  if ($first) $output .= "</data>\n";
  return $output;
}
 
?>
warhog at warhog dot net 12-Aug-2005 02:01
For very long arrays I have written a little function which formats an array quite nice and uses javascript for browsing it like a tree. The function is very customizable with the $style parameter.
For me it's of great use for browsing large array's, for example when those are used in language-files in some script and so on. It may even be used in "real" scripts for the "real" front-end, cause the tree can very easily be styled (look at the function or the outputted source and you'll see what i mean).

Here's the function:

<?php

function print_r_html($arr, $style = "display: none; margin-left: 10px;")
{ static $i = 0; $i++;
  echo "\n<div id=\"array_tree_$i\" class=\"array_tree\">\n";
  foreach($arr as $key => $val)
  { switch (gettype($val))
    { case "array":
        echo "<a onclick=\"document.getElementById('";
        echo array_tree_element_$i."').style.display = ";
        echo "document.getElementById('array_tree_element_$i";
        echo "').style.display == 'block' ?";
        echo "'none' : 'block';\"\n";
        echo "name=\"array_tree_link_$i\" href=\"#array_tree_link_$i\">".htmlspecialchars($key)."</a><br />\n";
        echo "<div class=\"array_tree_element_\" id=\"array_tree_element_$i\" style=\"$style\">";
        echo print_r_html($val);
        echo "</div>";
      break;
      case "integer":
        echo "<b>".htmlspecialchars($key)."</b> => <i>".htmlspecialchars($val)."</i><br />";
      break;
      case "double":
        echo "<b>".htmlspecialchars($key)."</b> => <i>".htmlspecialchars($val)."</i><br />";
      break;
      case "boolean":
        echo "<b>".htmlspecialchars($key)."</b> => ";
        if ($val)
        { echo "true"; }
        else
        { echo "false"; }
        echo  "<br />\n";
      break;
      case "string":
        echo "<b>".htmlspecialchars($key)."</b> => <code>".htmlspecialchars($val)."</code><br />";
      break;
      default:
        echo "<b>".htmlspecialchars($key)."</b> => ".gettype($val)."<br />";
      break; }
    echo "\n"; }
  echo "</div>\n"; }

?>

The function as it is now does not support the $return parameter as print_r does and will create an endless loop like print_r did in php-versions < 4.0.3 when there is an element which contains a reference to a variable inside of the array to print out :-/

I've tested it with PHP 5.0.6 and PHP 4.2.3 - no problems except those already mentioned.

please e-mail me if you've got a solution for the problems i've mentioned, i myself are not able to solve them 'cause i don't know how the hell i can find out whether a variable is a reference or not.
general at NOSPAMbugfoo dot com 20-Jan-2005 10:23
You can't use print_r($var, TRUE) inside a function which is a callback from ob_start() or you get the following error:
Fatal error: print_r(): Cannot use output buffering in output buffering display handlers