PHP spaceship operator less space equals more

This operator is designed to compare two expressions. It returns -1, 0, or 1 if $ a, respectively, is less than, equal to, or greater than $ b. The comparison is made in accordance with the rules of comparing PHP types.

<? php
// Integers
echo 1 <=> 1; // 0
echo 1 <=> 2; // -one
echo 2 <=> 1; // one

// Rational
echo 1.5 <=> 1.5; // 0
echo 1.5 <=> 2.5; // -one
echo 2.5 <=> 1.5; // one

// Strings
echo "a" <=> "a"; // 0
echo "a" <=> "b"; // -one
echo "b" <=> "a"; // one
?>