spl_object_hash

(PHP 5 >= 5.2.0, PHP 7)

spl_object_hash — Return hash id for given object

Description

string spl_object_hash ( object $obj )

This function returns a unique identifier for the object. This id can be used as a hash key for storing objects, or for identifying an object, as long as the object is not destroyed. Once the object is destroyed, its hash may be reused for other objects.

Parameters

object: Any object.

Return Values

A string that is unique for each currently existing object and is always the same for each object.

Examples

Example #1 A spl_object_hash() example


<?php
$id = spl_object_hash($object);
$storage[$id] = $object;
?>

Notes

Note:
When an object is destroyed, its hash may be reused for other objects.

User Contributed Notes

planetbeing

8 years ago


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.

mjs at beebo dot org

2 years ago


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

7 years ago


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;
    }
}

?>