Changing from MySQL to MySQLi. Select Inside Function in a Class does not work

Question

This is a simple problem but for some reason I am not seeing it. I am changing a piece of code from MySQL to MySQLi. The problem is that when I use the new MySQLi code, the select does not work.

I am showing three pieces of code. 1- The Index.php file including the codes 2. The Connect.php file showing how I connect to the DB 3. The Redirect.php class code using a function that is failing.

Inside the Redirect.php at the bottom, I have included the OLD code that works and the NEW code that does not work. All I see in the difference is that the new code is using the $con to communicate to the DB and I've tried global $con and it also fails. Please, I need your help. Can you let me know what I am doing wrong. Thanks.

<?php 
/*******************************/
/*  HERE IS THE INDEX.PHP FILE */
/*******************************/
session_start();
    include("connection.php");
    include("redirect.php");
    $log=new redirect();
    $log->check_logged();               
    $theme=$log->get_theme();
    echo 'This is the Website Theme: ' . $theme . '<br>';
    exit;
?>

<?php 
/**************************************************/
/* HERE IS THE CONNECTION.PHP CODE BEING INCLUDED */
/**************************************************/
$con = mysqli_init( );
if (!$con)
    {
        die("ERROR: MySQLi Initialed failed");
    }

if (!mysqli_real_connect($con, SERVERNAME,USERNAME,PASSWORD,DATABASENAME, NULL, NULL, MYSQL_CLIENT_INTERACTIVE))
    {
        die("MySQLi Real Connect Error: " . mysqli_connect_error());
    }
?>

<?php 
/**************************************************/
/* HERE IS THE REDIRECT.PHP CODE BEING INCLUDED */
/**************************************************/
class redirect
{
    function __construct()
    {   }

    function check_logged()
    {
        if(isset($_SESSION['member_id']) && $_SESSION['member_id']!="")
        {
            if(isset($_GET['loginad']) && $_GET['loginad']==1)
                header('location:'.SITEADDRESS_MEMBER.'memberoverview.php?loginad=1');
            if(isset($_GET['surfad']) && $_GET['surfad']==1)
                header('location:'.SITEADDRESS_MEMBER.'memberoverview.php?surfad=1');   
            else
                header('location:'.SITEADDRESS_MEMBER.'memberoverview.php');
        }
    }

    function get_theme()
    {
        /************************************************/
        /* HERE IS THE OLD REDIRECT.PHP CODE THAT WORKS */
        /************************************************/
        $result = mysql_query("select * from theme where status='yes'");
        if(mysql_num_rows($result)>0)
        {
            $data=mysql_fetch_array($result);
            return $data['theme_name'];
        }


        /********************************************************************/
        /* HERE IS THE NEW REDIRECT.PHP CODE BEING TESTED THAT DOESN'T WORK */
        /********************************************************************/
        $result = mysqli_query($con, "select * from theme where status='yes'")
        if(mysqli_num_rows($result)>0)
        {
            $data=mysqli_fetch_array($result, MYSQLI_ASSOC);
            return $data['theme_name'];
        }
    }
}
?>

How redirect::get_theme is supposed to access to var `$con` ? Its not in his scope. — ThinkTank, Oct 12 '15 at 14:44

AbraCadaver · Accepted Answer · 2015-10-12T14:50:09.347

0

There are other approaches, but the main issue is that $con is not avilable in the class. You can pass into the constructor, set it and use $this->con within the class:

include("connection.php"); // $con is defined here
$log = new redirect($con); // pass it to __construct()

class redirect
{
    public $con;

    function __construct($con) // accept it here
    {
        $this->con = $con;     // set it here
    }

    function get_theme()
    {
        // use it here
        $result = mysqli_query($this->con, "select * from theme where status='yes'");
    }
}

edited Oct 12 '15 at 14:50

answered Oct 12 '15 at 14:44

AbraCadaver

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The problem with this solution is that TPdeveloper will need to rewrite rewrite every constructors and instance of objects using mysqli_query – ThinkTank Oct 12 '15 at 15:01
Are you the one who put a -1 to my answer ? – ThinkTank Oct 12 '15 at 15:01
No, but I'll make it -2. – AbraCadaver Oct 12 '15 at 15:03
And can you tell me why ? – ThinkTank Oct 12 '15 at 15:06
Only because you were asking :-) – AbraCadaver Oct 12 '15 at 15:06
I was asking because i like to know when and why my answers are not pertinent. And there was no comment joining my -1 so I tried to figure out why. – ThinkTank Oct 12 '15 at 15:10
Some do that. If it was me I would most likely leave a comment. – AbraCadaver Oct 12 '15 at 17:28

ThinkTank · Answer 2 · 2015-10-12T14:54:38.913

You can use a singleton to have only one connection and easy to access when you need it :

class connection{

    private $con = null;

    public static function getCon()
    {
        if(null === $this->con)
        {

            $con = mysqli_init( );
            if (!$con)
            {
                die("ERROR: MySQLi Initialed failed");
            }

            if (!mysqli_real_connect($con, SERVERNAME,USERNAME,PASSWORD,DATABASENAME, NULL, NULL, MYSQL_CLIENT_INTERACTIVE))
            {
                die("MySQLi Real Connect Error: " . mysqli_connect_error());
            }

            $this->con = $con;
        }

        return $this->con;
    }
}

Then call it when you need it

function get_theme()
{
    /********************************************************************/
    /* HERE IS THE NEW REDIRECT.PHP CODE BEING TESTED THAT DOESN'T WORK */
    /********************************************************************/
    $result = mysqli_query(connection::getCon(), "select * from theme where status='yes'")
    if(mysqli_num_rows($result)>0)
    {
        $data=mysqli_fetch_array($result, MYSQLI_ASSOC);
        return $data['theme_name'];
    }
}

For information you can use mysqli in POO mode. I would recommend it coz you could easily return directly the mysqli object rather than just a $con

Changing from MySQL to MySQLi. Select Inside Function in a Class does not work

2 Answers2