recursion function and its own stack frame

recursion.php

<?php
function rDemo($n, $level = 1): void {
	$indent = str_repeat("    ", $level - 1);
	echo $indent . ' => Entering level ' . $level . "(n={$n})" . PHP_EOL;
	
	if ($n <= 0) {
		echo $indent . "Base case reached at level " . $level . " (n = " . $n . ")" . PHP_EOL;
		return;
	}
	rDemo($n - 1, $level + 1);
	
	echo $indent . ' <= Returning from level ' . $level . "(n={$n})" . PHP_EOL;
}

rDemo(3);

Output:

=> Entering level 1(n=3)
     => Entering level 2(n=2)
         => Entering level 3(n=1)
             => Entering level 4(n=0)
            Base case reached at level 4 (n = 0)
         <= Returning from level 3(n=1)
     <= Returning from level 2(n=2)
 <= Returning from level 1(n=3)