PHP7 Spaceship 運算子的語法

PHP 7.x 後有新增一個比較的語法，可以依照比對 >、=、< 分別回傳 1、0、-1

PHP7 <=> Spaceship 運算子的語法

PHP7 之後，有新增 Spaceship operator 的操作語法：

• echo 2 <=> 1; // 1
• echo 2 <=> 2; // 0
• echo 2 <=> 3; // -1
• 更大數值也是一樣
  • echo 2 <=> -1; // 1
  • echo 2 <=> 4; // -1
• 用 if 來舉例
  • if ($a == $b) = 0
  • if ($a > $b) = 1
  • if ($a < $b) = -1

下述摘錄自此篇：PHP: Comparison Operators - Manual

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

// Floats
echo 1.5 <=> 1.5; // 0
echo 1.5 <=> 2.5; // -1
echo 2.5 <=> 1.5; // 1

// Strings
echo "a" <=> "a"; // 0
echo "a" <=> "b"; // -1
echo "b" <=> "a"; // 1
echo "a" <=> "aa"; // -1
echo "zz" <=> "aa"; // 1

// Arrays
echo [] <=> []; // 0
echo [1, 2, 3] <=> [1, 2, 3]; // 0
echo [1, 2, 3] <=> []; // 1
echo [1, 2, 3] <=> [1, 2, 1]; // 1
echo [1, 2, 3] <=> [1, 2, 4]; // -1

// Objects
$a = (object) ["a" => "b"];
$b = (object) ["a" => "b"];
echo $a <=> $b; // 0

$a = (object) ["a" => "b"];
$b = (object) ["a" => "c"];
echo $a <=> $b; // -1

$a = (object) ["a" => "c"];
$b = (object) ["a" => "b"];
echo $a <=> $b; // 1

// not only values are compared; keys must match
$a = (object) ["a" => "b"];
$b = (object) ["b" => "b"];
echo $a <=> $b; // 1
?>