Even wondered how to use recursion in PHP closures?

decrease_and_print.php

<?php

$decrease = function($self, $number) {
    if ($number >= 0) {
        echo $number . PHP_EOL;
        $self($self, --$number);
    } 
};

$decrease($decrease, 10);

In a similar vein, using use

<?php

$cnt = 5;

$f = function() use(&$cnt, &$f) {
    echo $cnt--,PHP_EOL;
    if ($cnt > 0)
        $f();
};

$f();

I think the use of use for the closure itself is probably cleaner because I don't then have to remember to pass the closure as an argument to itself every time I call it; though the $number value for this simple decrementer should really be passed as a standard argument in the initial call

Mark Baker pointed out you can pass the closure (as reference) in the use clause, making it more user friendly.

<?php

$decrease = function($number) use (&$decrease) {
    if ($number >= 0) {
        echo $number . PHP_EOL;
        $decrease(--$number);
    } 
};

$decrease(10);

oops, added my comment before refreshing the page :)

But you've cleaned up my example, by passing $number as a simple argument :)

:) and changing decrease inside decrease?

nightmare version

$decrease = function($number) use (&$decrease) {
    $oldDecrease = $decrease;
    $rand = rand($number/2, $number*2);
    if ($number !=  $rand) {
        echo $number . PHP_EOL;
        $decrease(--$number);
    } else {
        $decrease = function($number) use (&$decrease, &$oldDecrease) {
            $rand = rand($number/2, $number*2);
            if ($number ==  $rand) {
                echo $number . PHP_EOL;
                $decrease(--$number);
            } else {
                $oldDecrease($number*2);
            }
        };
    }
};

$decrease(10);