Solved

@mysql_query  and mysql_query whats the difference?

Posted on 2006-07-06
12
388 Views
Last Modified: 2013-12-12
hi

I have 2 scripts that do very similar things,  one has this line
  $ret = @mysql_query($sql);
and the other
  $ret = mysql_query($sql);

the SQL is for all puropses the same.  want to know what the @ mark means.  

michael
0
Comment
Question by:ussher
  • 6
  • 5
12 Comments
 
LVL 142

Expert Comment

by:Guy Hengel [angelIII / a3]
ID: 17049448
@ supresses that the page prints out a error message, so you can handle it (using mysql_error() )

@ can be used for ALL functions, not only mysql...
0
 
LVL 40

Accepted Solution

by:
Richard Quadling earned 100 total points
ID: 17049466
@ means suppress any non fatal errors.

In fact it may even suppress them!

If using @, normally the next line of code will be determining if the result is a failure (in context with the function).

e.g. (from my own DB class)

      private function MakeDBConnection($objKrypt)
            {
            $resResult = @odbc_pconnect($this->DSN, $this->sUser, $objKrypt->Dekrypt($this->sPassword));
            if ($resResult === False)
                  {
                  throw new class_DB_Exception(
                        class_DB_Exception::DB_ERROR_SERVER_CONNECT,
                        array(
                              $this->sServer
                              )
                        );
                  }
            return $resResult;
            }

As you can see the odbc_pconnect() function can be false. Normally this will output a message also. By using @ the message is not reported and I can still continue testing the result.
0
 
LVL 1

Author Comment

by:ussher
ID: 17049470
so if error reporting is turned off at the server level both statements are exactly the same?
0
DevOps Toolchain Recommendations

Read this Gartner Research Note and discover how your IT organization can automate and optimize DevOps processes using a toolchain architecture.

 
LVL 40

Expert Comment

by:Richard Quadling
ID: 17049487
I think so. But just because you can't see the error, doesn't mean the function hasn't worked!

Error suppression is not a route to take if you want to have a stable app.

0
 
LVL 40

Expert Comment

by:Richard Quadling
ID: 17049489
Too many negatives!

No error message does not mean the function HAS worked!
0
 
LVL 1

Author Comment

by:ussher
ID: 17049506
ok thanks.  for now i will remove it and see if there are any errors but once it gets to production i dont want clients seeing errors.

im a bit clearer at what im looking at now.

cheers
0
 
LVL 40

Expert Comment

by:Richard Quadling
ID: 17049527
No.

Wrong way round.

Keep it in and add a test to see if the returned value is the error value. In mysql_query()'s case that would be false.

$ret = @mysql_query($sql);
if (False === $ref)
 {
 // Then something went wrong. Depending upon the statement, you may be able to handle the error or not.
 }
else
 {
 // The query was executed successfully. I would now be checking the mysql_affected_rows() (for update/insert/delete) or mysql_num_rows() (for select) to make sure the query performed as I expected it to.
 }

0
 
LVL 1

Author Comment

by:ussher
ID: 17049570
ok thanks.  Ill get it printing something

if (False === $ref) why 3 equals signs?  I have seen == before and know what that menas but never 3.  does it have a different meaning?

michael
0
 
LVL 1

Author Comment

by:ussher
ID: 17049579
sorry. got it
 === identical operator

RTFM

thanks for your help

michael
0
 
LVL 40

Expert Comment

by:Richard Quadling
ID: 17049586
PHP is loosely typed.

This means that

0 == "0" == False

zero equals in value the string "0" equals in value False.

BUT === means equal in value AND type.

0 !== "0" !== False

0
 
LVL 40

Expert Comment

by:Richard Quadling
ID: 17049598
And the reason why you use False !== is that you want to ONLY test that the function returned a boolean True.

e.g.

strpos('ABC', 'A')

The answer is 0

But

<?php
if (False == strpos('ABC', 'A'))
 {
 echo 'A not present';
 }
?>

is clearly wrong.


<?php
if (False === strpos('ABC', 'A'))
 {
 echo 'A not present';
 }
?>

is the right way.

0
 
LVL 1

Author Comment

by:ussher
ID: 17049667
awesome.

im now one step closer to enlightenment. (had to get the manual out and looked up strpos)

thanks

michael

0

Featured Post

NAS Cloud Backup Strategies

This article explains backup scenarios when using network storage. We review the so-called “3-2-1 strategy” and summarize the methods you can use to send NAS data to the cloud

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
PHP installation issues 11 62
Seeking info on how to integrate RETS feed based MLS data into a WordPress site 5 49
maybe no no httpd.conf 6 47
PHP AJAX Wordpress 9 21
Developers of all skill levels should learn to use current best practices when developing websites. However many developers, new and old, fall into the trap of using deprecated features because this is what so many tutorials and books tell them to u…
Part of the Global Positioning System A geocode (https://developers.google.com/maps/documentation/geocoding/) is the major subset of a GPS coordinate (http://en.wikipedia.org/wiki/Global_Positioning_System), the other parts being the altitude and t…
Explain concepts important to validation of email addresses with regular expressions. Applies to most languages/tools that uses regular expressions. Consider email address RFCs: Look at HTML5 form input element (with type=email) regex pattern: T…
The viewer will learn how to count occurrences of each item in an array.

810 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question