Besides new features like type hinting for scalar datatypes or the optimized performance, PHP 7 also brings many new, useful language extensions, and finally the "spaceship operator" has made it into the world of PHP (Ruby and Perl programmers have known it for a long time). \($a <=> $b\) returns \(0\) if both operands are equal, \(1\) if the left one is larger and \(-1\) otherwise .
Therefore, this new operator corresponds to the signum function \(sgn(x-y)\) known from mathematics, so that already existing comparison operators can also be interpreted with the help of the new syntax:
| \($a < $b\) | \(($a <=> $b) === -1\) |
| \($a <= $b\) | \(($a <=> $b)\) !\(== 1\) |
| \($a == $b\) | \(($a <=> $b) === 0\) |
| \($a\) !\(= $b\) | \(($a <=> $b)\) !\(== 0\) |
| \($a >= $b\) | \(($a <=> $b)\) !\(== -1\) |
| \($a > $b\) | \(($a <=> $b) === 1\) |
Thus the same rules apply as for the comparison operators (e.g. \([1,2,3] <=>[1,2,1]\) is equal to \(1\)) .