Null coalescing operator in PHP7

In PHP7, a new feature is introduced, the null coalescing operator (??). Since there are a lot of situations where ternary expressions and isset() are used simultaneously in the PHP7 project, the new null merge operator can be used to replace the ternary operation. With isset () function, if the variable exists and is not null , the null coalescing operator will return its first operation number; otherwise its second operand is returned.

There are three ways to achieve the goal:

1.if...else statement

<?php
    if(isset($_GET[&#39;user&#39;]))
    {
       $username = $_GET[&#39;user&#39;];
    }else{
       $username = &#39;nobody&#39;;
    }
?>

2.Three Meta operator:

<?php
  $username = isset($_GET[&#39;user&#39;]) ? $_GET[&#39;user&#39;] : &#39;nobody&#39;;// 获取user参数的值(如果为空，则用&#39;nobody&#39;)
?>

3. Null coalescing operator:

<?php
  $username = $_GET[&#39;user&#39;] ?? &#39;nobody&#39;;/*如果变量是存在的并且不为 null ，则空合并运算符将返回它的第一个操作数；
                                        否则将返回其第二个操作数。*/
?>

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