The `@` is the error suppression operator in PHP.

&gt; PHP supports one error control
&gt; operator: the at sign (@). When
&gt; prepended to an expression in PHP, any
&gt; error messages that might be generated
&gt; by that expression will be ignored.

**See:**

 - [Error Control Operators][1]
 - [Bad uses of the @ operator][2]

###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);

  [1]: http://php.net/manual/en/language.operators.errorcontrol.php
  [2]: http://michelf.com/weblog/2005/bad-uses-of-the-at-operator/


It won&#39;t throw a warning if $_POST[&#39;hn&#39;] is not set.

All that means is that, if $_POST[&#39;hn&#39;] is not defined, then instead of throwing an error or warning, PHP will just assign NULL to $hn.  

It suppresses warnings if $_POST[&#39;something&#39;] is not defined.


I&#39;m answering 11 years later for completeness regarding modern php.

Since php 7.0, the [null coalescing operator][1] 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 &#39;var_dump($_POST[&quot;hn&quot;]);&#39;
    PHP Warning:  Undefined array key &quot;hn&quot; in Command line code on line 1
    NULL

The output with silencing warnings (`@`):

    $ php -r &#39;var_dump(@$_POST[&quot;hn&quot;]);&#39;
    NULL

Obtaining the same result with the modern null coalescing operator (`??`):

    $ php -r &#39;var_dump($_POST[&quot;hn&quot;] ?? null);&#39;
    NULL


  [1]: https://www.php.net/manual/en/migration70.new-features.php#migration70.new-features.null-coalesce-op

This is a relatively open question.  If I have built an application in a project in Eclipse and I then want to test this project, should I create the JUnit code within the same project or create a separate project.  For instance...

`ShopSystem` maybe the name of my main project - should I create a project called say, `ShopSystemTest`?

In general - how far &quot;away&quot; should the testing code be stored from the main project folder?  If I store the testing code within the main project and then export the main project as a runnable jar it will take the testing code with it, which isn&#39;t ideal...

Suggestions?

Eclipse junit testing in the same project

Why quicksort(or introsort), or any comparison-based sorting algorithm is more common than radix-sort? Especially for sorting numbers.

Radix-sort is not comparison based, hence may be faster than O(n*logn). In fact, it is O(k*n), where k is the number of bits used to represent each item. And the memory overhead is not critical, since you may choose the number of buckets to use, and required memory may be less than mergesort&#39;s requirements.

Does it have to do with caching? Or maybe accessing random bytes of integers in the array?

Why quicksort is more popular than radix-sort?

I&#39;ve seen function calls preceded with an at symbol to switch off warnings. Today I was skimming some code and found this:

    $hn = @$_POST[&#39;hn&#39;];

What good will it do here?




&#39;At&#39; symbol before variable name in PHP: @$_POST

I've seen function calls preceded with an at symbol to switch off warnings. Today I was skimming some code and found this:
<pre><code class="hljs language-ini">$hn = @$_POST['hn'];
</code></pre>
What good will it do here?

After calling the redirect function header, should I call exit or not?

    &lt;?php // fileA
    $urlFailToGoTo = &#39;/formerror.php&#39;;
    
    if (sth)
    {
       header(sprintf(&quot;Location: %s&quot;, $urlFailToGoTo));
       exit(); //should I call exit() here? or return?
    }
    
    ?&gt;

Thank you

php - Should I call exit() after calling Location: header?

I&#39;ve been writing PHP applications using PHP for a while in WAMP. Now I&#39;m installing PHP and Apache HTTP Server separately on my work PC. I&#39;ve installed PHP 5, and the latest Apache. I go to localhost and see it works!

Now I add a file called `test.php` which displays:

    &lt;?php
        phpinfo();
    ?&gt;

But in the browser it just displays plain text. Is there somewhere I have explicitly tell it to use PHP 5?



Why are my PHP files showing as plain text?

Please give me some real life examples when you had to use __destruct in your classes.

Php Destructors

I would like to write a function that takes in 3 characters and increments it and returns the newly incremented characters as a string.

I know how to increase a single letter to the next one but how would I know when to increase the second letters and then stop and then increase the first letter again to have a sequential  increase?

&gt; So if AAA is passed, return AAB. If
&gt; AAZ is passed return ABA (hard part).

I would appreciate help with the logic and what php functions will be useful to use.

Even better, has some done this already or there is a class available to do this??

Thanks all for any help

How to increment letters like numbers in PHP?

In JavaScript, you can define anonymous functions that are executed immediately:

    (function () { /* do something */ })()

Can you do something like that in PHP?

How do I immediately execute an anonymous function in PHP?

I can&#39;t seem to get any error message from PDO:

    #$dbh-&gt;setAttribute( PDO::ATTR_ERRMODE, PDO::ERRMODE_WARNING );
    try {
      $sth = $dbh-&gt;prepare(&#39;@$%T$!!!&#39;);
      print_r($sth);
      print_r($dbh-&gt;errorInfo());
    } catch (PDOException $e) {
        echo $e-&gt;getMessage();
    }

It is giving out only:

    PDOStatement Object
    (
        [queryString] =&gt; @$%T$!!!
    )
    Array
    (
        [0] =&gt; 00000
        [1] =&gt;
        [2] =&gt;
    )

setAttribute doesn&#39;t help anything.

It&#39;s PHP 5.3.3 Apache 2.0 Handler &lt;br/&gt;
PDO Driver for MySQL enabled &lt;br/&gt;
Client API version mysqlnd 5.0.7-dev - 091210 - $Revision: 300533 $

What can I do to get error information?


How to squeeze error message out of PDO?



I am trying to raise a Warning in Python without making the program crash / stop / interrupt.

I use the following simple function to check if the user passed a non-zero number to it. If so, the program should warn them, but continue as per normal. It should work like the code below, but should use class `Warning()`, `Error()` or `Exception()` instead of printing the warning out manually.

    def is_zero(i):
       if i != 0:
         print &quot;OK&quot;
       else:
         print &quot;WARNING: the input is 0!&quot;
       return i

If I use the code below and pass 0 to the function, the program crashes and the value is never returned. Instead, I want the program to continue normally and just inform the user that he passed 0 to the function.

    def is_zero(i):
       if i != 0:
         print &quot;OK&quot;
       else:
         raise Warning(&quot;the input is 0!&quot;)
       return i
I want to be able to test that a warning has been thrown testing it by unittest. If I simply print the message out, I am not able to test it with assertRaises in unittest.

Raise warning in Python without interrupting program

`set -e` (or a script starting with `#!/bin/sh -e`) is extremely useful to automatically bomb out if there is a problem. It saves me having to error check every single command that might fail.

How do I get the equivalent of this inside a function?

For example, I have the following script that exits immediately on error with an error exit status:

    #!/bin/sh -e
    
    echo &quot;the following command could fail:&quot;
    false
    echo &quot;this is after the command that fails&quot;

The output is as expected:

    the following command could fail:

Now I&#39;d like to wrap this into a function:

    #!/bin/sh -e

    my_function() {
        echo &quot;the following command could fail:&quot;
        false
        echo &quot;this is after the command that fails&quot;
    }
    
    if ! my_function; then
        echo &quot;dealing with the problem&quot;
    fi

    echo &quot;run this all the time regardless of the success of my_function&quot;

Expected output:

    the following command could fail:
    dealing with the problem
    run this all the time regardless of the success of my_function

Actual output:

    the following output could fail:
    this is after the command that fails
    run this all the time regardless of the success of my_function

(ie. the function is ignoring `set -e`)

This presumably is expected behaviour. My question is: how do I get the effect and usefulness of `set -e` inside a shell function? I&#39;d like to be able to set something up such that I don&#39;t have to individually error check every call, but the script will stop on encountering an error. It should unwind the stack as far as is needed until I do check the result, or exit the script itself if I haven&#39;t checked it. This is what `set -e` does already, except it doesn&#39;t nest.

I&#39;ve found [the same question][1] asked outside Stack Overflow but no suitable answer.


  [1]: http://www.unix.com/shell-programming-scripting/114716-strange-behaviour-set-e-functions.html

How do I get the effect and usefulness of &quot;set -e&quot; inside a shell function?

Is there a way to specify that when executing a sql script it stops when encountering the first error on the script, it usually continues, regardless of previous errors.


How can I stop a Postgres script when it encounters an error?

I&#39;m getting the above error and unable to resolve it.
I googled a bit but can&#39;t get rid of it.

Scenario:
---------

I have class `BudgetAllocate` whose property is `budget` which is of `double` type.

In my `dataAccessLayer`,

In one of my classes I am trying to do this:

    double.TryParse(objReader[i].ToString(), out bd.Budget);

Which is throwing this error:

&gt; Property or indexer may not be passed as an out or ref parameter at
&gt; compile time.

I even tried this:

    double.TryParse(objReader[i].ToString().Equals(DBNull.Value) ? &quot;&quot; : objReader[i].ToString(), out bd.Budget);

Everything else is working fine and references between layers are present.

A property or indexer may not be passed as an out or ref parameter

I am trying to execute a SQlite replace function, but use another field in the function.

    select  locationname + &#39;&lt;p&gt;&#39; from location;

In this snip, the result is a list of 0s. I would have expected   a string with the text from locationname and the `&#39;&lt;p&gt;&#39;` literals.



String concatenation does not work in SQLite

I have some JavaScript code:

    &lt;script type=&quot;text/javascript&quot;&gt;
    $(document).ready(function(){
      $(&#39;#calcular&#39;).click(function() {
        var altura2 = ((($(&#39;#ddl_altura&#39;).attr(&quot;value&quot;))/100)^2);
        var peso = $(&#39;#ddl_peso&#39;).attr(&quot;value&quot;);
        var resultado = Math.round(parseFloat(peso / altura2)*100)/100;
        if (resultado &gt; 0) {
          $(&#39;#resultado&#39;).html(resultado);
          $(&#39;#imc&#39;).show();
        };
      });
    });
    &lt;/script&gt;

What does the `^` (caret) symbol mean in JavaScript?

What does the ^ (caret) symbol do in JavaScript?

I&#39;ve always done this: `if ($foo !== $bar)`

But I realized that `if ($foo != $bar)` is correct too.

Double `=` still works and has always worked for me, but whenever I search PHP operators I find no information on double `=`, so I assume I&#39;ve always have done this wrong, but it works anyway. Should I change all my `!==` to `!=` just for the sake of it?



Not equal to != and !== in PHP

Why are there no `++` and `--` operators in Python?

Why are there no ++ and --​ operators in Python?

The pre/post increment/decrement operator (`++` and `--`) are pretty standard programing language syntax (for procedural and object-oriented languages, at least). 

Why doesn&#39;t Ruby support them? I understand you could accomplish the same thing with `+=` and `-=`, but it just seems oddly arbitrary to exclude something like that, especially since it&#39;s so concise and conventional. 

Example:

    i = 0    #=&gt; 0
    i += 1   #=&gt; 1
    i        #=&gt; 1
    i++      #=&gt; expect 2, but as far as I can tell, 
             #=&gt; irb ignores the second + and waits for a second number to add to i

I understand `Fixnum` is immutable, but if `+=` can just instanciate a new `Fixnum` and set it, why not do the same for `++`?

Is consistency in assignments containing the `=` character the only reason for this, or am I missing something?

Content Type	Original Author	Original Content on Stackoverflow
Question	Majid Fouladpour	View Question on Stackoverflow
Solution 1 - Php	Sarfraz	View Answer on Stackoverflow
Solution 2 - Php	Tyson of the Northwest	View Answer on Stackoverflow
Solution 3 - Php	SenorPuerco	View Answer on Stackoverflow
Solution 4 - Php	Hydrino	View Answer on Stackoverflow
Solution 5 - Php	Frédéric Marchal	View Answer on Stackoverflow

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

Php Problem Overview

Php Solutions

Solution 1 - Php

Solution 2 - Php

Solution 3 - Php

Solution 4 - Php

Solution 5 - Php

Why quicksort is more popular than radix-sort?

Eclipse junit testing in the same project

Attributions