The Subtle Point of Return in PHP

After the return statement is executed, the function will finish its work. That is: after return is executed, no further code will be executed.

See the example:

<?php
	function func($num) {
		return $num * $num;
		
		echo '!'; // this code will never execute
	}
	
	$res = func(3);
?>

This does not mean that a function must have only one return. But only one of them will be executed.

In the following example, depending on the value of the parameter, either the first or the second return will be executed:

<?php
	function func($num) {
		if ($num >= 0) {
			return '+';
		} else {
			return '-';
		}
	}
	
	echo func( 3); // will output '+'
	echo func(-3); // will output '-'
?>

What will be output to the screen as a result of executing the following code:

<?php
	function func($num) {
		return $num;
		
		$res = $num * $num;
		return $res;
	}
	
	echo func(3);
?>

Explain why.

What will each echo output as a result of executing the following code:

<?php
	function func($num) {
		if ($num <= 0) {
			return abs($num);
		} else {
			return $num * $num;
		}
	}
	
	echo func(10);
	echo func(-5);
?>

Explain why.

What will each echo output as a result of executing the following code:

<?php
	function func($num) {
		if ($num <= 0) {
			return abs($num);
		}
		
		return $num * $num;
	}
	
	echo func(10);
	echo func(-5);
?>

Explain why.