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Amit Merchant

Amit Merchant

A blog on PHP, JavaScript, and more

Remembering what spaceship operator do on comparison in PHP

PHP has introduced an operator called “spaceship opearator” (<=>) with the release of PHP7. What this spaceship operator do is compare two expressions i.e. its two operands, let’s say $a and $b, and returns -1, 0 or 1 when $a is respectively less than, equal to, or greater than $b.

Here’s some examples of the same.

// Integers
echo 1 <=> 1; // 0
echo 1 <=> 2; // -1
echo 2 <=> 1; // 1

// Floats
echo 1.5 <=> 1.5; // 0
echo 1.5 <=> 2.5; // -1
echo 2.5 <=> 1.5; // 1
// Strings
echo "a" <=> "a"; // 0
echo "a" <=> "b"; // -1
echo "b" <=> "a"; // 1

The trick

But it turns out a lot of us tend to forget the purpose of the operator more often. So, here’s a handy yet effective trick to remember what this operator do pretty quickly.

What you’d do is to replace the spaceship operator (<=>) with a minus sign (-). If the result is negative, 0 or positive, the expression will return -1, 0 or 1 respectively. As you can see, it’s now more easy to remember when an analogy comes into play.

…And that is also how you remember anything you want, in general.

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