(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
is_callable(mixed $value, bool $syntax_only = false, string &$callable_name = null): bool
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, strings, or arrays 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.
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https://www.php.net/manual/en/function.is-callable.php