(PHP 4, PHP 5, PHP 7)
is_string — 检测变量是否是字符串
如果 var 是 string 则返回 TRUE，否则返回 FALSE。
参见 is_bool()、is_int()、is_integer()、is_float()、is_real()、is_object() 和 is_array()。
As noted earlier, is_string() returns false on an object that has a __toString() method. Here is a simple way to do a check that will work:
<?php
// determine if the passed argument can be treated like a string.
function is_stringy($text) {
return (is_string($text) || (is_object($text) && method_exists($text, '__toString' ));
}
Using is_string() on an object will always return false (even with __toString()).
<?php
class B {
public function __toString() {
return "Instances of B() can be treated as a strings!\n";
}
}
$b = new B();
print($b); //Instances of B() can be treated as a strings!
print(is_string($b) ? 'true' : 'false'); //false
?>
The cool thing about this function is that it lets you be a lot more specific with your logic than you could have been before. And since I'm all about explicit control, when it comes to code, this one gets me all hot and bothered.
<?php
//Like this. You could also do the reverse of it.
if(is_string($variable) ) && !is_array($variable) ){
//Do something that appeals to your controlling nature.
}
?>
God bless those php dev guys for thinking of everything.
Be aware that this function could result into unwanted results if you check single chars in an array.
For instance:
You have a simple string and want to repeat this string evertime it ends.
<?php
for ($i=0; $i < strlen($string);$i++){
if(!is_string($key[$x]))
$x = 0;
echo $key[$x];
$x++;
}
?>
This will print you out the key, but won't iterate it since $x won't be reset. is_string function will give out true at element in that string, even if it doesn't exist. for instance is_string $key[1000] while your string is just 10chars long.
However this doesn't matter just use $key[$x] == '' instead.
Of course you won't use this to iterate a string, but you might come across something where this get useful, for instance for a en/decrypt engine.