SplObjectStorage
PHP Manual

SplObjectStorage::getHash

Calculate a unique identifier for the contained objects

Description

public string SplObjectStorage::getHash(object $object)

This method calculates an identifier for the objects added to an SplObjectStorage object.

The implementation in SplObjectStorage returns the same value as spl_object_hash.

The storage object will never contain more than one object with the same identifier. As such, it can be used to implement a set (a collection of unique values) where the quality of an object being unique is determined by the value returned by this function being unique.

Parameters

object

The object whose identifier is to be calculated.

Return Values

A string with the calculated identifier.

Errors/Exceptions

A RuntimeException is thrown when the returned value is not a string.

Examples

Example #1 SplObjectStorage::getHash example

<?php
class OneSpecimenPerClassStorage extends SplObjectStorage {
    public function getHash($o) {
        return get_class($o);
    }
}
class A {}

$s = new OneSpecimenPerClassStorage;
$o1 = new stdClass;
$o2 = new stdClass;
$o3 = new A;

$s[$o1] = 1;
//$o2 is considered equal to $o1 so the value is replaced
$s[$o2] = 2;
$s[$o3] = 3;

//these are considered equal to the objects before
//so they can be used to access the values stored under them
$p1 = new stdClass;
$p2 = new A;
echo $s[$p1], "\n";
echo $s[$p2], "\n";
?>

The above example will output something similar to:

2
3

See Also

  • spl_object_hash