A detailed explanation of the null merge operator in PHP, phpnull operator _php Tutorial

A detailed explanation of the null merge operator in PHP, phpnull operator

The null merge operator is a good thing, and with it we can easily get a parameter and provide a default value in case it is empty. For example, in JS can be used in | | To engage in:

function Setsomething (a) {  a = a | | ' Some-default-value ';  // ...}

And in PHP, unfortunately PHP's | | Always returns TRUE or FALSE, unable to do so.

PHP7 only formally joined the party?? This operator:

Get the value of the user parameter (if empty, use ' nobody ') $username = $_get[' user ']?? ' nobody ';//equivalent to: $username = isset ($_get[' user ')? $_get[' user ']: ' nobody ';

PHP7 estimate there is still a long time to use the production environment, there is no alternative in the current PHP5?

According to the study, there is a very convenient alternative:

Get the value of the user parameter (if empty, use ' nobody ') $username = @$_get[' user ']?: ' nobody ';//equivalent to: $username = isset ($_get[' user ')? $_get[' user ']: ' nobody ';

--Run this code: HTTPS://3V4L.ORG/ADUW8

Staring at the eyes, with the PHP7 of the previous example of the similar, mainly to the?? Replace for?:. What kind of a ghost is this? Actually this is (EXPR1)? (EXPR2): ellipsis mode for (EXPR3) expression:

An expression (EXPR1)? (EXPR2): (EXPR3) when EXPR1 evaluates to TRUE, the value is EXPR2, and the value is EXPR1 when the EXPR3 evaluates to FALSE.

From PHP 5.3, the middle part of the ternary operator can be omitted. Expression expr1?: Expr3 returns EXPR1 when EXPR1 evaluates to TRUE, otherwise returns EXPR3.

--http://php.net/manual/zh/language.operators.comparison.php

Of course, this alternative is not perfect-if there is no ' user ' in $_get, there will be a notice:undefined index:user error, so you need to use @ To suppress the error, or to turn off E_notice's error.

PS:PHP7 null merge operator Farewell Isset ()

The previous wording

$info = isset ($_get[' email ')? $_get[' email ': ' Noemail ';

Just write this right now.

$info = $_get[' email '?? Noemail;

You can also use this ligatures

$info = $_get[' email '?? $_post[' email '?? ' Noemail ';

Articles you may be interested in:

• C # null merge operator?? (double question mark) using the example

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