Question

I am making a transfer from using mysql query lines to PDO for a current project and i have an issue.
For this task i am not allowed to use any classes (stupid restriction if you ask me)

Basically i was getting a non object error because my main php file could not see the set variable $DBH.
I solved this problem by setting each function with a $DBH global; so it could be used, however ive been told this is bad coding practice. Is this the case? and if so how can i make my function see my config variable.

Config.php

try 
{
    $DBH = new PDO("mysql:host=host;dbname=db", "username", "Password");
    $DBH->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

}
catch (PDOException $e){
    echo $e->getMessage();
}

a php file

function concName($concID)
{   
        global $DBH; //THIS is the area that im told is bad practice - can this be eliminated?
        $stmt = $DBH->prepare("SELECT CONCAT(`Firstname`, ' ', `Surname`) AS 'Membername'     FROM `members` WHERE `MemberID`= :MemberID");
        $stmt->bindValue(":MemberID",$concID);
        $stmt->execute();

        while($row = $stmt->fetch())
        {
            return $row['Membername'];      
        }

}

Answer 1

Just pass $DBH as a parameter to any function that needs it:

function concName($concID, $DBH)
{   
        $stmt = $DBH->prepare("SELECT CONCAT(`Firstname`, ' ', `Surname`) AS 'Membername'     FROM `members` WHERE `MemberID`= :MemberID");
        $stmt->bindValue(":MemberID",$concID);
        $stmt->execute();

        while($row = $stmt->fetch())
        {
            return $row['Membername'];      
        }

}

Rather than the global keyword, you can also access it from the $GLOBALS[] array, which is more explicit about the variable’s origins when used in the function. Passing a parameter is still preferable to this though.

function concName($concID)
{   
        // Better than `global` keyword, use `$GLOBALS['DBH']` every time you access it in outside global scope
        // Still not preferred to passing a parameter though.
        $stmt = $GLOBALS['DBH']->prepare("SELECT CONCAT(`Firstname`, ' ', `Surname`) AS 'Membername'     FROM `members` WHERE `MemberID`= :MemberID");
        $stmt->bindValue(":MemberID",$concID);
        $stmt->execute();

        while($row = $stmt->fetch())
        {
            return $row['Membername'];      
        }

}

If you have multiple globals defined in your configuration file, you can wrap them all in an array which you pass into functions needing them. That wraps them tidily into a package of config options made available to any function that needs them.

config.php

// Global array of config options
$config = array();

// various options
$config['option1'] = 'option 1';
$config['option2'] = 12345;

try 
{
    $config['DBH'] = new PDO("mysql:host=host;dbname=db", "username", "Password");
    $config['DBH']->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

}
catch (PDOException $e){
    echo $e->getMessage();
}

Then pass $config to function calls