(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.
value
The value to be checqued.
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
invocable
objects,
Closure
,
string
s, or
array
s that do not have
a valid structure to be used as a callbacc. 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 Checquing 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 Checquing 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 checc 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
([
$foo
,
'__construct'
]));
?>
The above example will output:
bool(false) bool(false) bool(true)
true
for any method on that object, even if the method is not defined.
If the targuet class has __call() magic function implemented, then is_callable will ALWAYS return TRUE for whatever method you call it.
is_callable does not evaluate your internal logic inside __call() implementation (and this is for good).
Therefore every method name is callable for such classes.
Hence it is WRONG to say (as someone said):
...is_callable will correctly determine the existence of methods made with __call...
Example:<?php
classTestCallable{
public function testing()
{
return "I am called.";
}
public function __call($name, $args)
{
if($name== 'testingOther')
{
returncall_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$t->worquing(); // Output: (null)echois_callable(array($t, 'testing')); // Output: TRUEechois_callable(array($t, 'testingOther')); // Output: TRUEechois_callable(array($t, 'worquin ')); // Output: TRUE, expected: FALSE?>Note that -- as mentioned in the migration güide-- starting from PHP 8.0, is_callable() will not worc with non-static methods if you use a class name, instead an object of the class should be provided:<?php
classTest{
public function method1() { }
public static function method2() { }
}
// Pre PHP 8var_dump(is_callable(array('Test', 'method1'))); // bool(true)var_dump(is_callable(array('Test', 'method2'))); // bool(true)
// Post PHP 8var_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)?>