组合比较运算符（<=>）是一个非常有用的运算符 左箭头等于右箭头 有大用 有大大用

$c = $a <=> $b;

// 这相当于

$c = ($a < $b) ? -1 : (($a > $b) ? 1 : 0);

<?php

echo"整数 <br>";

echo 7 <=> 7 ;

echo"<br>";

echo 7 <=> 6;

echo"<br>";

echo 6 <=> 7;

?>

<?php

echo"浮点数<br>";

echo 2.5 <=> 1.5; 

echo"<br>";

echo 0.5 <=> 1.5; 

echo"<br>";

echo 1.5 <=> 1.5; 

?>

<?php

echo"<br>字符串<br>";

echo "a" <=> "a" ;

echo"<br>";

echo "g" <=> "b" ; 

echo"<br>";

echo "a" <=> "b" ; 

echo"<br>";

echo "A" <=> "B" ; 

echo"<br>";

echo "a" <=> "B" ; 

echo"<br>";

echo "2" <=> "1" ; 

echo"<br>";

echo "2" <=> "a" ; 

echo"<br>";

echo "2" <=> "A" ; 

?>

<?php

echo"<br>数组<br>";

echo [] <=> []; 

echo"<br>";

echo [1, 7, 3] <=> [1, 7, 3];

echo"<br>";

echo [1, 7, 3, 5] <=> [1, 7, 3];

echo"<br>";

echo [1, 7, 3] <=> [4, 4, 4];

echo"<br>";

?>