PHP函数method_exists检查类是否存在和与is_callable()的区别
PHP method_exists 检查类的方法是否存在
method_exists
method_exists — 检查类的方法是否存在
说明
bool method_exists ( object $object , string $method_name )
如果 method_name 所指的方法在 object 所指的对象类中已定义，则返回 TRUE，否则返回 FALSE。
Example #1 method_exists() 例子
以上例程会输出：<?php
$directory = new Directory('.');
var_dump(method_exists($directory,'read'));
?>bool(true)
PHP method_exists note #1
Just to mention it: both method_exists() and is_callable() return true for inherited methods:
<?php
class ParentClass {
function doParent() { }
}
class ChildClass extends ParentClass { }
$p = new ParentClass();
$c = new ChildClass();
// all return true
var_dump(method_exists($p, 'doParent'));
var_dump(method_exists($c, 'doParent'));
var_dump(is_callable(array($p, 'doParent')));
var_dump(is_callable(array($c, 'doParent')));
?>
PHP method_exists note #2
Using method_exists inside an object's __call() method can be very usefull if you want to avoid to get a fatal error because of a limit in function nesting or if you are calling methods that dont exist but need to continue in your application:
<?php
class Something
{
/**
* Call a method dynamically
*
* @param string $method
* @param array $args
* @return mixed
*/
public function __call($method, $args)
{
if(method_exists($this, $method)) {
return call_user_func_array(array($this, $method), $args);
}else{
throw new Exception(sprintf('The required method "%s" does not exist for %s', $method, get_class($this)));
}
}
}
?>
PHP method_exists note #3
As noted [elsewhere] method_exists() does not care about the existence of __call(), whereas is_callable() does:
<?php
class Test {
public function explicit( ) {
// ...
}
public function __call( $meth, $args ) {
// ...
}
}
$Tester = new Test();
var_export(method_exists($Tester, 'anything')); // false
var_export(is_callable(array($Tester, 'anything'))); // true
?>
PHP method_exists note #4
Be warned that the class must exist before calling method exists from an eval statement otherwise you will get a Signal Bus error.
PHP method_exists note #5
It wasn't spelled out but could be inferred: method_exists() also works on interfaces.
<?php
var_dump(method_exists("Iterator", "current"));
// bool(true)
?>
PHP method_exists note #6
If you want to check in a class itself if a method is known you may do so with magic variable __CLASS__
<?php
class A{
__construct($method){
return method_exists(__CLASS__,$method);
}
private function foo(){
}
}
$test = new A('foo');
//should return true
?>
You might also use the method describe below with <?php in_array() ?>trick but I consider this one here easier and more readable and well, the way it is intended toi be done ;)
PHP method_exists note #7
Hi,
Here is a useful function that you can use to check classes methods access e.g whether it is public, private or static or both..
here it goes:
<?php
// Example class
class myClass {
private $private1;
static $static1;
public $public1;
public function publ() {
}
private function priv() {
}
private static function privstatic() {
}
public static function publstatic() {
}
static function mytest() {
}
}
// The function uses the reflection class that is built into PHP!!!
// The purpose is to determine the type of a certain method that exi
function is_class_method($type="public", $method, $class) {
// $type = mb_strtolower($type);
$refl = new ReflectionMethod($class, $method);
switch($type) {
case "static":
return $refl->isStatic();
break;
case "public":
return $refl->isPublic();
break;
case "private":
return $refl->isPrivate();
break;
}
}
var_dump(is_class_method("static", "privstatic", "myClass")); // true - the method is private and also static..
var_dump(is_class_method("private", "privstatic", "myClass")); // true - the method is private and also static..
var_dump(is_class_method("private", "publstatic", "myClass")); // False the methos is public and also static not private
// you get the idea.. I hope this helps someone..
?>
PHP method_exists note #8
This function is case-insensitive (as is PHP) and here is the proof:
<?php
class A {
public function FUNC() { echo '*****'; }
}
$a = new A();
$a->func(); // *****
var_dump(method_exists($a, 'func')); // bool(true)
?>
PHP method_exists note #9
As mentioned before, is_callable and method_exists report all methods callable even if they are private/protected and thus actually not callable. So instead of those functions you may use following work-around which reports methods as supposed to.
<?php
class Foo1 {
public function bar() {
echo "I'm private Foo1::bar()";
}
}
class Foo2 {
private function bar() {
echo "I'm public Foo2::bar()";
}
}
$f1=new Foo1;
$f2=new Foo2;
if(is_callable(array($f1,"bar"))) {
echo "Foo1::bar() is callable";
} else {
echo "Foo1::bar() isn't callable";
}
if(is_callable(array($f2,"bar"))) {
echo "Foo2::bar() is callable";
} else {
echo "Foo2::bar() isn't callable";
}
if(in_array("bar",get_class_methods($f1))) {
echo "Foo1::bar() is callable";
} else {
echo "Foo1::bar() isn't callable";
}
if(in_array("bar",get_class_methods($f2))) {
echo "Foo2::bar() is callable";
} else {
echo "Foo2::bar() isn't callable";
}
?>
output
Foo1::bar() is callable (correct)
Foo2::bar() is callable (incorrect)
Foo1::bar() is callable (correct)
Foo2::bar() isn't callable (correct)
?>
在编程中，我们有的时候需要判断某个类中是否包含某个方法，除了使用反射机制，PHP还提供了method_exists()和is_callable()方法进行判断。那么两则区别是什么呢？
已知类文件如下：
class Student{
private $alias=null; private $name=''; public function __construct($name){
$this->name=$name;
} private function setAlias($alias){
$this->alias=$alias;
} public function getName(){
return $this->name;
}
}12345678910111213当方法是private，protected类型的，method_exists会报错，is_callable会返回false。
实例
下面是判断某一对象中是否存在方法getName
通过method_exists实现
$xiaoming=new Student('xiaoming');if (method_exists($xiaoming, 'getName')) {
echo 'exist';
}else{ echo 'not exist';
}exit();1234567输出exist
通过is_callable实现
$xiaoming=new Student('xiaoming');if (is_callable(array($xiaoming, 'getName'))) {
echo 'exist';
}else{ echo 'not exist';
}exit();1234567输出exist
下面是判断某一对象中是否存在方法setAlias
当使用method_exists的时候报错如下
当使用is_callable的时候，输出not exist
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