'At' symbol before variable name in PHP: @$_POST

Question

I've seen function calls preceded with an at symbol to switch off warnings. Today I was skimming some code and found this:

$hn = @$_POST['hn'];

What good will it do here?

possible duplicate of [Reference - What does this symbol mean in PHP?](http://stackoverflow.com/questions/3737139/reference-what-does-this-symbol-mean-in-php) — Quentin, Dec 19 '11 at 16:22

score 75 · Accepted Answer · edited Oct 23 '16 at 00:51

75

The @ is the error suppression operator in PHP.

PHP supports one error control operator: the at sign (@). When prepended to an expression in PHP, any error messages that might be generated by that expression will be ignored.

See:

Update:

In your example, it is used before the variable name to avoid the E_NOTICE error there. If in the $_POST array, the hn key is not set; it will throw an E_NOTICE message, but @ is used there to avoid that E_NOTICE.

Note that you can also put this line on top of your script to avoid an E_NOTICE error:

error_reporting(E_ALL ^ E_NOTICE);

edited Oct 23 '16 at 00:51

Harmen

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answered Aug 23 '10 at 20:44

Sarfraz

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But it is used before a variable name not a function. – Majid Fouladpour Aug 23 '10 at 20:45
if `hn` is not set in $_POST, it will throw a notice (`Notice: undefined index...`). `@` will suppress that notice. But using `@` is just wrong. – robertbasic Aug 23 '10 at 20:49
Understand now. Thank you Sarfaraz. Hope your people could put the flood behind them soon. – Majid Fouladpour Aug 23 '10 at 20:57
"PHP6 Note" —— that makes **no** sense. – salathe Aug 23 '10 at 21:25
2

Something that others forgot to mention is that besides ignoring the NOTICE, the variable will be set to `NULL`. – Yani Jul 18 '19 at 10:19

score 11 · Answer 2 · answered Aug 23 '10 at 20:47

11

It won't throw a warning if $_POST['hn'] is not set.

answered Aug 23 '10 at 20:47

Tyson of the Northwest

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score 7 · Answer 3 · answered Aug 23 '10 at 20:48

7

All that means is that, if $_POST['hn'] is not defined, then instead of throwing an error or warning, PHP will just assign NULL to $hn.

answered Aug 23 '10 at 20:48

SenorPuerco

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score 3 · Answer 4 · edited Dec 10 '15 at 20:06

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It suppresses warnings if $_POST['something'] is not defined.

edited Dec 10 '15 at 20:06

Peter Mortensen

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answered Aug 23 '10 at 20:51

Hydrino

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score 0 · Answer 5 · answered May 11 '22 at 06:16

I'm answering 11 years later for completeness regarding modern php.

Since php 7.0, the null coalescing operator is a more straightforward alternative to silencing warnings in that case. The ?? operator was designed (among other things) for that purpose.

Without @, a warning is shown:

$ php -r 'var_dump($_POST["hn"]);'
PHP Warning:  Undefined array key "hn" in Command line code on line 1
NULL

The output with silencing warnings (@):

$ php -r 'var_dump(@$_POST["hn"]);'
NULL

Obtaining the same result with the modern null coalescing operator (??):

$ php -r 'var_dump($_POST["hn"] ?? null);'
NULL

'At' symbol before variable name in PHP: @$_POST

5 Answers5

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