(PHP 4, PHP 5, PHP 7)
get_parent_class — 返回对象或类的父类名
如果 obj
是对象，则返回对象实例 obj
所属类的父类名。
如果 obj
是字符串，则返回以此字符串为名的类的父类名。此功能是在
PHP 4.0.5 中增加的。
Note:
自 PHP 5 起，如果在对象的方法内调用，则
obj为可选项。
Example #1 使用 get_parent_class()
<?php
class dad {
function dad()
{
// implements some logic
}
}
class child extends dad {
function child()
{
echo "I'm " , get_parent_class($this) , "'s son\n";
}
}
class child2 extends dad {
function child2()
{
echo "I'm " , get_parent_class('child2') , "'s son too\n";
}
}
$foo = new child();
$bar = new child2();
?>
以上例程会输出：
I'm dad's son I'm dad's son too
参见 get_class() 和 is_subclass_of()。
objectThe tested object or class name
Returns the name of the parent class of the class of which
object is an instance or the name.
Note:
If the object does not have a parent or the class given does not exist
FALSEwill be returned.
If called without parameter outside object, this function returns FALSE.
| 版本 | 说明 |
|---|---|
| Before 5.1.0 |
If called without parameter outside object, this function would have
returned NULL with a warning.
|
| Since 5.0.0 |
The object parameter is optional if called
from the object's method.
|
| Since 4.0.5 |
If object is a string, returns the name of the
parent class of the class with that name.
|
Example #2 Using get_parent_class()
<?php
class dad {
function dad()
{
// implements some logic
}
}
class child extends dad {
function child()
{
echo "I'm " , get_parent_class($this) , "'s son\n";
}
}
class child2 extends dad {
function child2()
{
echo "I'm " , get_parent_class('child2') , "'s son too\n";
}
}
$foo = new child();
$bar = new child2();
?>
以上例程会输出：
I'm dad's son I'm dad's son too
Note that from PHP 5.5 you can also use `parent::class` from within a method, e.g.
<?php
function child()
{
echo "I'm ", parent::class, "'s son\n";
}
?>
Looks a bit tidier and technically probably more optimal, as it avoids a function call lookup.
An output of the entire inheritance chain using closures, recursion, and OOP
class ParentClass {
public static function getChain() {
$chain = null;
return $function = function($className='') use (& $chain, & $function) {
if (empty($className))
$className = static::class;
if (empty($chain))
$chain = $className;
$parent = get_parent_class($className);
if ($parent !== false) {
$chain .= " > {$parent}";
return $function($parent);
}
return $chain;
};
}
}
class Child extends ParentClass {}
class SubChild extends Child {}
class Sub2 extends SubChild {}
class Sub3 extends Sub2 {}
class Sub4 extends Sub3 {}
class Sub5 extends Sub4 {}
class Sub6 extends Sub5 {}
class Sub7 extends Sub6 {}
printf("%s\n", Sub7::getChain()());
$getChain = Sub7::getChain();
printf("%s\n", $getChain('Sub3'));
Output is:
Sub7 > Sub6 > Sub5 > Sub4 > Sub3 > Sub2 > SubChild > Child > ParentClass
Sub3 > Sub2 > SubChild > Child > ParentClass
You can use this function to find common parent of multiple objects or classes.
<?php
/**
* Returns name of the first (in class hierarchy) common parent class of all provided objects or classes.
* Returns FALSE when common class is not found.
*
* @param mixed $objects Array that can contain objects or class names.
* @return mixed
*/
function get_first_common_parent($objects) {
$common_ancestors = null;
foreach($objects as $object) {
if (is_object($object)) {
$class_name = get_class($object);
} else {
$class_name = $object;
}
$parent_class_names = array();
$parent_class_name = $class_name;
do {
$parent_class_names[] = $parent_class_name;
} while($parent_class_name = get_parent_class($parent_class_name));
if ($common_ancestors === null) {
$common_ancestors = $parent_class_names;
} else {
$common_ancestors = array_intersect($common_ancestors, $parent_class_names);
}
}
return reset($common_ancestors);
}
?>
Example:
<?php
class A {
}
class B extends A {
}
class D extends B {
}
class E extends B {
}
class C extends A {
}
class F extends C {
}
class G extends F {
}
class H {
}
//returns "A"
get_first_common_parent(array('G', 'E'));
//returns "F"
get_first_common_parent(array(new G(), 'F'));
//returns false (no common parent)
get_first_common_parent(array('C', 'H'));
//returns false (non-existent class provided)
get_first_common_parent(array(new B(), 'X'));
?>
I wrote a simple function doing the reverse thing: get the children:
<?php
function get_child($instance, $classname) {
$class = $classname;
$t = get_class($instance);
while (($p = get_parent_class($t)) !== false) {
if ($p == $class) {
return $t;
}
$t = $p;
}
return false;
}
abstract class A {
function someFunction() {
return get_child($this, __CLASS__);
}
}
class B extends A {
}
class C extends B {
}
$c = new C();
echo $c->someFunction(); //displays B
?>
"'If called without parameter outside object' What on earth does that mean?"
There are two places this could be called:
1. From within a member function of an object. In this case, it may be called with no parameters and will return the parent class of the object owning the member function. (If the parameter is included, then it will return the parent class of the specified class as normal.)
2. From outside an object (i.e., global or function scope). In this case, PHP doesn't know what class you're talking about if you don't include a parameter, so it returns FALSE. (But, of course, it works if you specify the class with the parameter.)
PHP (4 at least, dunno about 5) stores classnames in lower case, so:
<?PHP
class Foo
{
}
class Bar extends Foo
{
}
echo get_parent_class('Bar');
echo "\n";
echo get_parent_class('bar');
?>
will output:
foo
foo
If the argument obj is a string and the class is not defined, then the function returns FALSE.
If the argument obj is an object created from a class with no ancestors (or a string representing a class with no ancestors), then the function returns FALSE.