(PHP 4 >= 4.0.6, PHP 5, PHP 7, PHP 8)
is_callable — Verify that a value can be called as a function from the current scope
Verifies that value is a callable ,
or that it can be called using the
call_user_func() function.
valueThe value to be checked.
syntax_only
If set to true the function only verifies that
value might be a function or method. It will
reject any values that are not invokable objects,
Closure , string s, or array s that do not have
a valid structure to be used as a callback. A valid callable array
has 2 entries, the first of which is an object
or a string, and the second a string.
callable_name
Receives the "callable name", e.g.
"SomeClass::someMethod". Note, however, that despite
the implication that SomeClass::someMethod() is a
callable static method, this is not the case.
Example #1 Checking whether a string can be called as a function
<?php
function someFunction() {}
$functionVariable = 'someFunction';
var_dump(is_callable($functionVariable, false, $callable_name));
var_dump($callable_name);
?>The above example will output:
bool(true) string(12) "someFunction"
Example #2 Checking whether an array can be called as a function
<?php
class SomeClass
{
public function someMethod() {}
}
$anObject = new SomeClass();
$methodVariable = [$anObject, 'someMethod'];
var_dump(is_callable($methodVariable, true, $callable_name));
var_dump($callable_name);
?>The above example will output:
bool(true) string(21) "SomeClass::someMethod"
Example #3 is_callable() and constructors
Despite the fact that constructors are the methods that are called when
an object is created, they are not static methods and
is_callable() will return false for them. It's not
possible to use is_callable() to check if a class can
be instantiated from the current scope.
<?php
class Foo
{
public function __construct() {}
public function foo() {}
}
var_dump(
is_callable(['Foo', '__construct']),
is_callable(['Foo', 'foo'])
);
$foo = new Foo();
var_dump(is_callable([$foo, '__construct']));
?>The above example will output:
bool(false) bool(false) bool(true)
true for any method on that object, even if the method is not defined.
If the target class has __call() magic function implemented, then is_callable will ALWAYS return TRUE for whatever method you call it.
is_callable does not evaluate your internal logic inside __call() implementation (and this is for good).
Therefore every method name is callable for such classes.
Hence it is WRONG to say (as someone said):
...is_callable will correctly determine the existence of methods made with __call...
Example:
<?php
class TestCallable
{
public function testing()
{
return "I am called.";
}
public function __call($name, $args)
{
if($name == 'testingOther')
{
return call_user_func_array(array($this, 'testing'), $args);
}
}
}
$t = new TestCallable();
echo $t->testing(); // Output: I am called.
echo $t->testingOther(); // Output: I am called.
echo $t->working(); // Output: (null)
echo is_callable(array($t, 'testing')); // Output: TRUE
echo is_callable(array($t, 'testingOther')); // Output: TRUE
echo is_callable(array($t, 'working')); // Output: TRUE, expected: FALSE
?>Note that -- as mentioned in the migration guide-- starting from PHP 8.0, is_callable() will not work with non-static methods if you use a class name, instead an object of the class should be provided:
<?php
class Test
{
public function method1() { }
public static function method2() { }
}
// Pre PHP 8
var_dump(is_callable(array('Test', 'method1'))); // bool(true)
var_dump(is_callable(array('Test', 'method2'))); // bool(true)
// Post PHP 8
var_dump(is_callable(array('Test', 'method1'))); // bool(false)
var_dump(is_callable(array('Test', 'method2'))); // bool(true)
var_dump(is_callable(array(new Test, 'method1'))); // bool(true)
?>