Ternary Operator in PHP

Let's say we have the following code that checks whether the user is already 18 years old or not:

<?php
	$age = 17;
	
	if ($age >= 18) {
		$adult = true;
	} else {
		$adult = false;
	}
	
	var_dump($adult);
?>

As you can see, the if-else construct is only needed to write a specific value to the variable $adult. For such tasks, when in a condition we only set one variable, there is a shorter solution using the so-called ternary operator.

Its syntax is as follows:

<?php
	variable = condition ? value1 : value2;
?>

The operator works as follows: if the condition is true, then value1 is returned, otherwise - value2. Let's rewrite the code from the very beginning of the lesson using the ternary operator:

<?php
	$age = 17;
	$adult = $age >= 18 ? true: false;
	var_dump($adult);
?>

By the way, you can avoid writing the result to a variable and immediately output it via var_dump:

<?php
	$age = 17;
	var_dump( $age >= 18 ? true: false );
?>

The ternary operator should only be used in the simplest cases, as its use makes the code harder to understand.

Let a variable $num be given, which can be either negative or positive. Write into the variable $res the number 1 if the variable $num is greater than or equal to zero, and the number -1 if the variable $num is less than zero.