<?php

    $x = array("a" => "red", "b" => "green"); 

    $y = array("c" => "blue", "d" => "yellow"); 

    $z = $x + $y; // $x 和 $y 数组合并

    var_dump($z);

    var_dump($x == $y);

    var_dump($x === $y);

     var_dump($x != $y);

    var_dump($x <> $y);

    var_dump($x !== $y);

    ?>