CODEWITHSUNDEEP
phpanonymous-function
Jage
Jage

Reputation: 8086

php is_function() to determine if a variable is a function

I was pretty excited to read about anonymous functions in php, which let you declare a variable that is function easier than you could do with create_function. Now I am wondering if I have a function that is passed a variable, how can I check it to determine if it is a function? There is no is_function() function yet, and when I do a var_dump of a variable that is a function::

$func = function(){
    echo 'asdf';
};
var_dump($func);

I get this:

object(Closure)#8 (0) { }

Any thoughts on how to check if this is a function?

Upvotes: 100

Views: 53037

Answers (5)

Andrey Izman
Andrey Izman

Reputation: 1914

In php valid callables can be functions, name of functions (strings) and arrays of the forms ['className', 'staticMethod'] or [$object, 'method'], so to detect only functions need to exclude strings and arrays:

function isFunction($callable) {
    return $callable && !is_string($callable) && !is_array($callable) && is_callable($callable);
}

Upvotes: 0

Artemiy StagnantIce Alexeew
Artemiy StagnantIce Alexeew

Reputation: 862

function is_function($f) {
    return is_callable($f) && !is_string($f);
}

Upvotes: 2

Brilliand
Brilliand

Reputation: 13714

If you only want to check whether a variable is an anonymous function, and not a callable string or array, use instanceof.

$func = function()
{  
    echo 'asdf';  
};

if($func instanceof Closure)
{
    // Will be true.
}

Anonymous functions (of the kind that were added in PHP 5.3) are always instances of the Closure class, and every instance of the Closure class is an anonymous function.

There's another type of thing in PHP that could arguably be considered a function, and that's objects that implement the __invoke magic method. If you want to include those (while still excluding strings and arrays), use method_exists($func, '__invoke'). This will still include closures, since closures implement __invoke for consistency.

Upvotes: 33

Jon Benedicto
Jon Benedicto

Reputation: 10582

Use is_callable to determine whether a given variable is a function. For example:

$func = function()
{  
    echo 'asdf';  
};

if( is_callable( $func ) )
{
    // Will be true.
}

Upvotes: 159

Gumbo
Gumbo

Reputation: 655189

You can use function_exists to check there is a function with the given name. And to combine that with anonymous functions, try this:

function is_function($f) {
    return (is_string($f) && function_exists($f)) || (is_object($f) && ($f instanceof Closure));
}

Upvotes: 38

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