PHP spaceship operator (combined comparison operator)

PHP 7 newly added spaceship operator (combined comparison operator) is used to compare two expressions$a and $b, if $a is less than, equal to, or greater than $b, it returns -1, 0 or 1 respectively.

Example

<?php
// 整型比较
print( 1 <=> 1);echo "<br/>";
print( 1 <=> 2);echo "<br/>";
print( 2 <=> 1);echo "<br/>";
print(PHP_EOL);
// 浮点型比较
print( 1.5 <=> 1.5);echo "<br/>";
print( 1.5 <=> 2.5);echo "<br/>";
print( 2.5 <=> 1.5);echo "<br/>";
print(PHP_EOL);
// 字符串比较
print( "a" <=> "a");echo "<br/>";
print( "a" <=> "b");echo "<br/>";
print( "b" <=> "a");echo "<br/>";
?>

The above program execution output result is: