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Simple tip for OOP MySQLi in PHP

The purpose of this tutorial is to show you how I use PHP's OOP MySQLi in larger projects.


For larger projects, I like to separate out the connection to the MySQLi in another file. We'll call the class db_connect.php since that's what most books seem to reference it as.

db_connect.php--
















I'll take it another step further and create a class that's going to make it simple for me to call other classes. I'll call
it ClassInitialization. This class will only contain one method className() and it's purpose will be to initialize other classes.

class_initialization.php
--
















As is evident from the above code, the className() method requires 2 parameters: the name of the class that you want initialized and an optional file location parameter. It'll then require_once() the file and return the new ClassName object.

To put the 2 classes that we've created together, you'll need to create a third class that will do something specific for your website. In this case I'm creating a class that will provide the user with further details on selected products. I'll name the class PageItemDetails.

item_details.php
--


First thing that you may notice is the extends of the ClassInitialization class. We want to be able to use that className() method.

We go ahead and initialize a $_mysqli property globally instead of locally from every method.

The first example of how effective the ClassInitialization class is can be seen in the __construct() method. You call the className() method and pass the name of the db_connect class called DatabaseConnection and you pass it's location db_connect.php.

If you reference the code in ClassInitialization, you'll see that it'll require_once() the db_connect.php file and initialize the DatabaseConnection object.

From there you are free to use the $_mysqli property in all of the subsequent methods.


From the above code, you'll notice that it's just a regular OOP MySQLi statement.  You generate the $sql statement; you prepare the $sql statement; you bind the parameters to the statement; You execute the statement and grab the result.

Here I use the className() method again to call the error page. The only other notable portion of the code is the $smt->close(). You'll also want to close the $_mysqli, but since it's used in most methods within this class, you'll want to close it last. I just create a __destruct() method to end it.


Hope that helps optimize your code. To conclude, the key portions that you'll want to pay attention to is the __construct() and __destruct() methods to optimize your code. It's up to you whether you want to utilize the ClassInitialization class.

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