(PHP 5, PHP 7)
array_udiff — 用回调函数比较数据来计算数组的差集
使用回调函数比较数据，计算数组的不同之处。和 array_diff() 不同的是，前者使用内置函数进行数据比较。
array1第一个数组。
array2第二个数组。
value_compare_func回调对照函数。
在第一个参数小于，等于或大于第二个参数时，该比较函数必须相应地返回一个小于，等于或大于 0 的整数。
返回 array1 里没有出现在其他参数里的所有值。
Example #1 array_udiff() 使用 stdClass 对象的例子
<?php
// Arrays to compare
$array1 = array(new stdclass, new stdclass,
new stdclass, new stdclass,
);
$array2 = array(
new stdclass, new stdclass,
);
// Set some properties for each object
$array1[0]->width = 11; $array1[0]->height = 3;
$array1[1]->width = 7; $array1[1]->height = 1;
$array1[2]->width = 2; $array1[2]->height = 9;
$array1[3]->width = 5; $array1[3]->height = 7;
$array2[0]->width = 7; $array2[0]->height = 5;
$array2[1]->width = 9; $array2[1]->height = 2;
function compare_by_area($a, $b) {
$areaA = $a->width * $a->height;
$areaB = $b->width * $b->height;
if ($areaA < $areaB) {
return -1;
} elseif ($areaA > $areaB) {
return 1;
} else {
return 0;
}
}
print_r(array_udiff($array1, $array2, 'compare_by_area'));
?>
以上例程会输出：
Array
(
[0] => stdClass Object
(
[width] => 11
[height] => 3
)
[1] => stdClass Object
(
[width] => 7
[height] => 1
)
)
Example #2 array_udiff() 使用 DateTime 对象的例子
<?php
class MyCalendar {
public $free = array();
public $booked = array();
public function __construct($week = 'now') {
$start = new DateTime($week);
$start->modify('Monday this week midnight');
$end = clone $start;
$end->modify('Friday this week midnight');
$interval = new DateInterval('P1D');
foreach (new DatePeriod($start, $interval, $end) as $freeTime) {
$this->free[] = $freeTime;
}
}
public function bookAppointment(DateTime $date, $note) {
$this->booked[] = array('date' => $date->modify('midnight'), 'note' => $note);
}
public function checkAvailability() {
return array_udiff($this->free, $this->booked, array($this, 'customCompare'));
}
public function customCompare($free, $booked) {
if (is_array($free)) $a = $free['date'];
else $a = $free;
if (is_array($booked)) $b = $booked['date'];
else $b = $booked;
if ($a == $b) {
return 0;
} elseif ($a > $b) {
return 1;
} else {
return -1;
}
}
}
// Create a calendar for weekly appointments
$myCalendar = new MyCalendar;
// Book some appointments for this week
$myCalendar->bookAppointment(new DateTime('Monday this week'), "Cleaning GoogleGuy's apartment.");
$myCalendar->bookAppointment(new DateTime('Wednesday this week'), "Going on a snowboarding trip.");
$myCalendar->bookAppointment(new DateTime('Friday this week'), "Fixing buggy code.");
// Check availability of days by comparing $booked dates against $free dates
echo "I'm available on the following days this week...\n\n";
foreach ($myCalendar->checkAvailability() as $free) {
echo $free->format('l'), "\n";
}
echo "\n\n";
echo "I'm busy on the following days this week...\n\n";
foreach ($myCalendar->booked as $booked) {
echo $booked['date']->format('l'), ": ", $booked['note'], "\n";
}
?>
以上例程会输出：
I'm available on the following days this week... Tuesday Thursday I'm busy on the following days this week... Monday: Cleaning GoogleGuy's apartment. Wednesday: Going on a snowboarding trip. Friday: Fixing buggy code.
Note: 注意本函数只检查了多维数组中的一维。当然，可以用 array_udiff($array1[0], $array2[0], "data_compare_func"); 来检查更深的维度。
Note that the compare function is used also internally, to order the arrays and choose which element compare against in the next round.
If your compare function is not really comparing (ie. returns 0 if elements are equals, 1 otherwise), you will receive an unexpected result.
Quick example for using array_udiff to do a multi-dimensional diff
Returns values of $arr1 that are not in $arr2
<?php
$arr1 = array( array('Bob', 42), array('Phil', 37), array('Frank', 39) );
$arr2 = array( array('Phil', 37), array('Mark', 45) );
$arr3 = array_udiff($arr1, $arr2, create_function(
'$a,$b',
'return strcmp( implode("", $a), implode("", $b) ); ')
);
print_r($arr3);
?>
Output:
Array
(
[0] => Array
(
[0] => Bob
[1] => 42
)
[2] => Array
(
[0] => Frank
[1] => 39
)
)
1
Hope this helps someone
Note that php does the string conversion *before* sending the values to the callback function.
It is not stated, by this function also diffs array1 to itself, removing any duplicate values...
Re: "convoluted"
I think the point being made is that array_udiff() can be used not only for comparisons between homogenous arrays, as in your example (and definitely the most common need), but it can be used to compare heterogeneous arrays, too.
Consider:
<?php
function compr_1($a, $b) {
$aVal = is_array($a) ? $a['last_name'] : $a;
$bVal = is_array($b) ? $b['last_name'] : $b;
return strcasecmp($aVal, $bVal);
}
$aEmployees = array(
array('last_name' => 'Smith',
'first_name' => 'Joe',
'phone' => '555-1000'),
array('last_name' => 'Doe',
'first_name' => 'John',
'phone' => '555-2000'),
array('last_name' => 'Flagg',
'first_name' => 'Randall',
'phone' => '666-1000')
);
$aNames = array('Doe', 'Smith', 'Johnson');
$result = array_udiff($aEmployees, $aNames, "compr_1");
print_r($result);
?>
Allowing me to get the "employee" that's not in the name list:
Array ( [2] => Array ( [last_name] => Flagg [first_name] => Randall [phone] => 666-1000 ) )
Something interesting to note, is that the two arguments to the compare function don't correspond to array1 and array2. That's why there has to be logic in it to handle that either of the arguments might be pointing to the more complex employee array. (Found this out the hard way.)
I think the example given here using classes is convoluting things too much to demonstrate what this function does.
array_udiff() will walk through array_values($a) and array_values($b) and compare each value by using the passed in callback function.
To put it another way, array_udiff() compares $a[0] to $b[0], $b[1], $b[2], and $b[3] using the provided callback function. If the callback returns zero for any of the comparisons then $a[0] will not be in the returned array from array_udiff(). It then compares $a[1] to $b[0], $b[1], $b[2], and $b[3]. Then, finally, $a[2] to $b[0], $b[1], $b[2], and $b[3].
For example, compare_ids($a[0], $b[0]) === -5 while compare_ids($a[1], $b[1]) === 0. Therefore, $a[1] is not returned from array_udiff() since it is present in $b.
<?
$a = array(
array(
'id' => 10,
'name' => 'John',
'color' => 'red',
),
array(
'id' => 20,
'name' => 'Elise',
'color' => 'blue',
),
array(
'id' => 30,
'name' => 'Mark',
'color' => 'red',
),
);
$b = array(
array(
'id' => 15,
'name' => 'Nancy',
'color' => 'black',
),
array(
'id' => 20,
'name' => 'Elise',
'color' => 'blue',
),
array(
'id' => 30,
'name' => 'Mark',
'color' => 'red',
),
array(
'id' => 40,
'name' => 'John',
'color' => 'orange',
),
);
function compare_ids($a, $b)
{
return ($a['id'] - $b['id']);
}
function compare_names($a, $b)
{
return strcmp($a['name'], $b['name']);
}
$ret = array_udiff($a, $b, 'compare_ids');
var_dump($ret);
$ret = array_udiff($b, $a, 'compare_ids');
var_dump($ret);
$ret = array_udiff($a, $b, 'compare_names');
var_dump($ret);
?>
Which returns the following.
In the first return we see that $b has no entry in it with an id of 10.
<?
array(1) {
[0]=>
array(3) {
["id"]=>
int(10)
["name"]=>
string(4) "John"
["color"]=>
string(3) "red"
}
}
?>
In the second return we see that $a has no entry in it with an id of 15 or 40.
<?
array(2) {
[0]=>
array(3) {
["id"]=>
int(15)
["name"]=>
string(5) "Nancy"
["color"]=>
string(5) "black"
}
[3]=>
array(3) {
["id"]=>
int(40)
["name"]=>
string(4) "John"
["color"]=>
string(6) "orange"
}
}
?>
In third return we see that all names in $a are in $b (even though the entry in $b whose name is 'John' is different, the anonymous function is only comparing names).
<?
array(0) {
}
?>
Very easy way of achieving a case-insensitive version of array_diff (or indeed array_diff_assoc, array_intersect or any of these types of functions which have a similar function that takes a callback function as one of their parameters):
array_udiff($array1, $array2, 'strcasecmp');
This works because strcasecmp() compares two strings case-insensitively, as compared to the array_diff() which compares two strings by using the == operator, which is case-sensitive.
This functionality is now implemented in the PEAR package PHP_Compat.
More information about using this function without upgrading your version of PHP can be found on the below link:
http://pear.php.net/package/PHP_Compat