Simple recursive function is not working

Question

I'm trying to run a recursive function, but it doesn't work properly. I don't see any errors in my code, so maybe this is just not possible with PHP?

<?php

$herpNum = 0;

function herp() {
    if ($herpNum == 22) {
        echo "done";
    } else {
        $herpNum = $herpNum+1;
        echo $herpNum."<br/>";
        herp();
    }
}

herp();

?>

when I run this, the result is just a long list of 1.

Answer 1

Because $herpNum isn't in the same scope as the function, so it's creating a new $herpNum inside the function which defaults to 0 and then is adding 1 to it.

You could either pass it in as an arguement or have it as a global variable.

$herpNum = 0;

function herp($herpNum) {
    if ($herpNum == 22) {
        echo "done";
    } else {
        $herpNum = $herpNum+1;
        echo $herpNum."<br/>";
        herp($herpNum);
    }
}

herp($herpNum);

or

$herpNum = 0;

function herp() {
    global $herpNum;

    if ($herpNum == 22) {
        echo "done";
    } else {
        $herpNum = $herpNum+1;
        echo $herpNum."<br/>";
        herp();
    }
}

herp();

Answer 2

It's because you're not passing in the parameter $herpnum into the function.

<?php

$herpNum = 0;

function herp($herpNum) {
    if ($herpNum == 22) {
        echo "done";
    } else {
        $herpNum = $herpNum+1;
        echo $herpNum."<br/>";
        herp($herpNum);
    }
}

herp($herpNum);

?>

That should work