PHP spaceship operator (combined comparison operators)

PHP 7’s newly added spaceship operator (combined comparison operator) is used to compare two expressions $a and $b, if $a When it 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/>";
echo "<br/>"; // PHP_EOL 为换行符

// 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/>";
echo "<br/>";

// 字符串比较
print( "a" <=> "a");echo "<br/>";
print( "a" <=> "b");echo "<br/>";
print( "b" <=> "a");echo "<br/>";
?>

The execution output of the above program is:

0
-1
1

0
-1
1

0
-1
1