(PHP 5 >= 5.2.0)
spl_object_hash — 返回指定对象的hash id
$obj
)本函数为指定对象返回一个唯一标识符。这个标识符可用于作为保存对象或区分不同对象的hash key。
object
Any object.
字符串，对于每个对象它都是唯一的，并且对同一个对象它总是相同。
Example #1 A spl_object_hash() example
<?php
$id = spl_object_hash($object);
$storage[$id] = $object;
?>
Note:
When an object is destroyed, its hash may be reused for other objects.
mjs at beebo dot org (2013-05-16 11:20:42)
Note that given two different objects spl_object_hash() can return values that look very similar, and in fact both the most significant *and* least significant digits are likely to be identical! e.g. "000000003cc56d770000000007fa48c5" and "000000003cc56d0d0000000007fa48c5".
Therefore (especially if using this function for debugging), you may wish to pass the hash into a cryptographic hash function like md5() to get to facilitate visual comparisons, and make it more likely that the first few or last few digits are unique.
md5("000000003cc56d770000000007fa48c5") -> "619a799747d348fa1caf181a72b65d9f"
md5("000000003cc56d0d0000000007fa48c5") -> "ae964bc912281e7804fe5a88b4546cb2"
Rafael M. Salvioni (2008-12-04 11:01:26)
The follow function is a implementation of the PHP?s function spl_object_hash(), unavailable in versions less 5.2.0.
But, the algorithm of this function is different of the original PHP?s function.
(Sorry... my english is very bad...)
<?php
if (!function_exists('spl_object_hash')) {
/**
* Returns the hash of the unique identifier for the object.
*
* @param object $object Object
* @author Rafael M. Salvioni
* @return string
*/
function spl_object_hash($object)
{
if (is_object($object)) {
ob_start(); var_dump($object); $dump = ob_get_contents(); ob_end_clean();
if (preg_match('/^object\(([a-z0-9_]+)\)\#(\d)+/i', $dump, $match)) {
return md5($match[1] . $match[2]);
}
}
trigger_error(__FUNCTION__ . "() expects parameter 1 to be object", E_USER_WARNING);
return null;
}
}
?>
planetbeing (2007-07-05 16:40:22)
Note that the contents (properties) of the object are NOT hashed by the function, merely its internal handle and handler table pointer. This is sufficient to guarantee that any two objects simultaneously co-residing in memory will have different hashes. Uniqueness is not guaranteed between objects that did not reside in memory simultaneously, for example:
var_dump(spl_object_hash(new stdClass()), spl_object_hash(new stdClass()));
Running this alone will usually generate the same hashes, since PHP reuses the internal handle for the first stdClass after it has been dereferenced and destroyed when it creates the second stdClass.