recursion - Anonymous recursive PHP functions

Question

Is it possible to have a PHP function that is both recursive and anonymous? This is my attempt to get it to work, but it doesn't pass in the function name.

$factorial = function( $n ) use ( $factorial ) {
    if( $n <= 1 ) return 1;
    return $factorial( $n - 1 ) * $n;
};
print $factorial( 5 );

I'm also aware that this is a bad way to implement factorial, it's just an example.

Answer 1

In order for it to work, you need to pass $factorial as a reference

$factorial = function( $n ) use ( &$factorial ) {
    if( $n == 1 ) return 1;
    return $factorial( $n - 1 ) * $n;
};
print $factorial( 5 );