Find out if a method exists in a static class

问题:

I want to check is a function exists in a library that I am creating, which is static. I've seen function and method_exists, but haven't found a way that allows me to call them in a relative context. Here is a better example:

class myClass{
    function test1()
    {
        if(method_exists("myClass", "test1"))
        {
            echo "Hi";
        }
    }
    function test2()
    {
        if(method_exists($this, "test2"))
        {
            echo "Hi";
        }
    }
    function test3()
    {
        if(method_exists(self, "test3"))
        {
            echo "Hi";
        }
    }
}
// Echos Hi
myClass::test1();
// Trys to use 'self' as a string instead of a constant
myClass::test3();
// Echos Hi
$obj = new myClass;
$obj->test2();

I need to be able to make test 3 echo Hi if the function exists, without needing to take it out of static context. Given the keyword for accessing the class should be 'self', as $this is for assigned classes.

回答1:

get_called_class() was introduced in PHP 5.3, and will return the "Late Static Binding" class name:

class myClass{
    public static function test()
    {
        if(method_exists(get_called_class(), "test"))
        {
                echo get_called_class().'::test()';
        }
    }
}

class subClass extends myClass{}

subClass::test() // should print "subClass::test()"

---

The get_class() function, which as of php 5.0.0 does not require any parameters if called within a class will return the name of the class in which the function was declared (e.g., the parent class):

class myClass{
    public static function test()
    {
        if(method_exists(get_class(), "test"))
        {
                echo get_class().'::test()';
        }
    }
}

class subClass extends myClass{}

subClass::test() // prints "myClass::test()"

The __CLASS__ magic constant does the same [link].

class myClass{
    public static function test()
    {
        if(method_exists(__CLASS__, "test"))
        {
                echo __CLASS__.'::test()';
        }
    }
}

class subClass extends myClass{}

subClass::test() // prints "myClass::test()"

回答2:

Update:

Ahh, apologies. I was temporarily blind :) You'll want to use the magic constant __CLASS__

e.g.

if (method_exists(__CLASS__, "test3")) { echo "Hi"; }

回答3:

for all situations… the best usage would be…

if method_exist(…) && is_callable(…)

For testing example:

class Foo {
  public function PublicMethod() {}
  private function PrivateMethod() {}
  public static function PublicStaticMethod() {}
  private static function PrivateStaticMethod() {}
}

$foo = new Foo();

$callbacks = array(
  array($foo, 'PublicMethod'),
  array($foo, 'PrivateMethod'),
  array($foo, 'PublicStaticMethod'),
  array($foo, 'PrivateStaticMethod'),
  array('Foo', 'PublicMethod'),
  array('Foo', 'PrivateMethod'),
  array('Foo', 'PublicStaticMethod'),
  array('Foo', 'PrivateStaticMethod'),
);

foreach ($callbacks as $callback) {
  var_dump($callback);
  var_dump(method_exists($callback[0], $callback[1])); // 0: object / class name, 1: method name
  var_dump(is_callable($callback));
  echo str_repeat('-', 40), "n";
}

Source here