Why are the results different when using <=> operator in PHP 7 and PHP 8?

Question

Why are the results different when using <=> operator in PHP 7 and PHP 8?

In PHP 7:

echo 76 <=> '76 trombones';  // displays 0

In PHP 8:

echo 76 <=> '76 trombones';  // displays -1

Answer 1

PHP 8 changed the way non-strict comparison between numbers and non-numeric strings work.

<=> is a non-strict comparison.

The values in your example, 76 and '76 trombones' evaluated as equal in PHP 7 because the string was cast to a number for the comparison, and (int) '76 trombones' is 76.

Now in PHP 8, the number is cast to string for the comparison instead.