(PHP 5 >= 5.4.0)
SplObjectStorage::getHash — Calculate a unique identifier for the contained objects
$object
)This method calculates an identifier for the objects added to an SplObjectStorage object.
The implementation in SplObjectStorage returns the same value as spl_object_hash().
The storage object will never contain more than one object with the same identifier. As such, it can be used to implement a set (a collection of unique values) where the quality of an object being unique is determined by the value returned by this function being unique.
object
The object whose identifier is to be calculated.
A string with the calculated identifier.
A RuntimeException is thrown when the returned value is not a string.
Example #1 SplObjectStorage::getHash() example
<?php
class OneSpecimenPerClassStorage extends SplObjectStorage {
public function getHash($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";
?>
以上例程的输出类似于：
2 3
aron dot duby at gmail dot com (2012-12-17 07:09:07)
This also appears to be the function which gets used within the contains() function, so if all the objects you are storing already have a unique id you can overwrite this function with your own class.
<?php
class UserStorage extends SPLObjectStorage{
public function getHash($obj){
return $obj->id;
}
}
$us = new UserStorage();
$user1 = new User(1);
$user2 = new User(2);
$us->attach($user1);
$us->attach($user2);
$me = new User(2);
// the following would normally fail since they are two separate objects
// but it works now with our extended getHash()
$us->contains($me);
?>