How to put mysql inside a php function?

Question

I have problem about putting mysql into a function showMsg(). The mysql is working fine if it is not wrapped by function showMsg(), but when I wrap it with function showMsg(), it gives error message "Warning: mysql_query(): supplied argument is not a valid". How to put mysql inside a php function? Below is my codes :

<?php    
function showMsg(){   
        $query2 = "SELECT id, message, username, datetime FROM messageslive ORDER BY id DESC LIMIT 20";
        $result2 = mysql_query($query2,$connection) or die (mysql_error());
        confirm_query($result2);
        $num = mysql_num_rows($result2); 
        while($msginfo = mysql_fetch_array($result2)){
            echo $msginfo['message'];
            echo $msginfo['username'];
        }
}

<div>
   <?php showMsg(); ?>
</div>
?>

score 9 · Answer 1 · edited May 23 '17 at 10:29

9

Never use global.
Pass $connection into your function as an argument.
Logic and representation should be separated.
Read about MVC: here or here.
Global variables are evil, never use it. If someone suggests it - ignore all their answers.

edited May 23 '17 at 10:29

Community

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answered May 24 '11 at 00:06

OZ_

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never knew i can do that. I have follow your suggestion, i am using function parameter instead of global :) – zac1987 May 24 '11 at 00:17

score 6 · Accepted Answer · answered May 23 '11 at 23:52

6

You probably need:

global $connection;

(Inside the function, that is.)

See Variable Scope

answered May 23 '11 at 23:52

Alex Howansky

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perfect. Thank you very much :) – zac1987 May 23 '11 at 23:57
I voted down for recommending globals. globals very often lead to sloppy code with unexpected results. – Jim Ford May 24 '11 at 03:44

Tyrick · Answer 3 · 2011-05-24T00:13:52.203

As everyone mentioned, the issue has to do with variable scoping. Instead of add global $connection; you could consider a more OOP approach and consider:

A: passing the $connection variable into the function.

B: placing related functions in a class and pass the DB connection into the Class constructor. for example:

class YourClass  {

   private $connection;

   public function __construct($connection) {
       $this->connection = $connection;
   }

   public function showMsg(){   
        $query2 = "SELECT id, message, username, datetime FROM messageslive ORDER BY id DESC LIMIT 20";
        $result2 = mysql_query($query2,$this->connection) or die (mysql_error());
        confirm_query($result2);
        $num = mysql_num_rows($result2); 
        while($msginfo = mysql_fetch_array($result2)){
            echo $msginfo['message'];
            echo $msginfo['username'];
        }
   }

}

I don't have enough rep to comment. But I also like OZ_'s answer :)

OMG, I have very less knowledge about Class and Object things. May I know any benefits if I use class instead of passing $connection to function parameters? — zac1987, May 24 '11 at 00:21
@Zac1987 It can take a bit of time to learn OOP techniques, but a quick google search on OOP + PHP should bring back something interesting. Trust me learning OOP will benefit you so much in the long run as well as make your code more manageable and clean. — Kenny Cason, May 24 '11 at 00:28

score 2 · Answer 4 · answered May 23 '11 at 23:53

2

$connection variable has no value assigned. The following code should solve your problem (add it at the beginning of the function):

global $connection;

But you should be aware of the fact, that using globals is not a good idea and you may want to:

(preferably) pass $connection variable within the parameter of the function, or
move $connection declaration from outside the function just into the function (if it does not cause additional problems), or
redeclare $connection variable within the function (again: if it will not cause additional problems),

answered May 23 '11 at 23:53

Tadeck

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I was wondering where should i put global $connection; Thanks for pointing me :) – zac1987 May 23 '11 at 23:59
No problem :) It should be placed before you use `$connection` variable - if you put it at the beginning of the function, this should meet this requirement ;) – Tadeck May 24 '11 at 00:02

score 0 · Answer 5 · answered May 23 '11 at 23:53

0

Because variables are local to functions. You need to add this inside your function:

global $connection;

answered May 23 '11 at 23:53

gnxtech3

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score -2 · Answer 6 · answered May 23 '11 at 23:58

-2

Simply put, functions ignore outside variables due to variable scope. You must let the declare the variable as being from the outside by using global or you can send $connection through a parameter.

answered May 23 '11 at 23:58

Yoshiyahu

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How to put mysql inside a php function?

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