PHP Callables Examples

anonymous functions (Closures)

<?php

/*
 * Functions without a name, created using the `function` keyword without a name or using the `fn` syntax.
 */
 
$func = fn (string $v): int => strlen($v);
 
var_dump(
    is_callable($func),
    is_callable($func(...)),
);
 
// https://3v4l.org/BOua9

built-in functions

<?php

/*
 * PHP’s internal functions like `strlen()` or `strtolower()`.
 */
 
var_dump(
    is_callable('strlen'),
    is_callable(strlen(...)),
);

// https://3v4l.org/PnFL3

invokable objects

<?php

/*
 * Objects that implement the `__invoke()` magic method, allowing them to be called as functions.
 */
 
class Foo
{
    public function __invoke()
    {
    }
}

$foo = new Foo();

var_dump(
    is_callable($foo),
    is_callable([$foo, '__invoke']),
    is_callable($foo(...)),
);

// https://3v4l.org/fBKu3

object methods

<?php

/*
 * Methods within a class, which can be static or instance methods.
 */
 
class Foo
{
    public function ping()
    {
    }
    
    public static function pong()
    {
    }
}

$foo = new Foo();

var_dump(
    is_callable([$foo, 'ping']),
    is_callable($foo->ping(...)),

    is_callable('Foo::pong'),
    is_callable([Foo::class, 'pong']),
    is_callable(Foo::pong(...)),
);

// https://3v4l.org/MdJDLm

user-defined functions

<?php

/*
 * Regular functions defined using the `function` keyword.
 */
 

function foo(): string
{
  return 'bar';
}

var_dump(
    is_callable('foo'),
    is_callable(foo(...)),
);

// https://3v4l.org/tlWtD