How To Use OOP In PHP For Real Life Examples

[JustinK101]

So I am sitting and trying to figure out, how making classes in php, and using OOP in php would be useful. I do a lot of PHP + MySQL.

 

Let me give an example of the kind of things I do, which are common, and perhaps somebody could provide some OOP examples:

 

Lets assume we have the following MySQL table schema.

 

Customers

id
first_name
last_name
company_name

 

Orders

id
associated_customer_id
number_of_products
price_per_product

 

If I want to pull all customers I would simply do something like:

 

$sql = "SELECT * FROM customers";
$result = mysql_query($sql) or die(mysql_error());
while($row = mysql_fetch_object($result))
{
   echo 'First Name: ' . $row->first_name;
   echo 'Last Name: ' . $row->last_name;
   //And So Forth
}

 

Now it would be cool if I could simply create a new 'customers' class object and then call a class member or simply GET and SET class member variables. I am just not sure how to go about doing it.

 

Thanks for the help.

 

[JustinK101]

Ok, so here is what I came up with.

 

class Customer
{
	var $id;
	var $first_name;
	var $last_name;
	var $company_name;

	//Constructor - Creates a customer with all properites set to null.
	function Customer()
	{
		$this->id = NULL;
		$this->first_name = NULL;
		$this->last_name = NULL;
		$this->company_name = NULL; 
	}

	//Overloaded Constructor - Creates a customer with all properties set from the customer id.
	function Customer($id)
	{
		$sql = "SELECT * FROM customers WHERE customer_id = " . $id	. " LIMIT 1";
		$result = mysql_query($sql) or die(mysql_error());
		while($row = mysql_fetch_assoc($result))
		{
			$this->id = $id;
			$this->first_name = $row['first_name'];
			$this->last_name = $row['last_name'];
			$this->company_name = $row['company_name'];
		}
	}
}

//Create and instanciate of the customer object
$myCustomer = new Customer();

//Create and instanciate of the customer object
$myCustomer2 = new Customer(121);

 

I am not understanding the benfit of this? It took like 5 times as long, and a lot more typing. Pehaps somebody could explain further.

[trq]

I am not understanding the benfit of this? It took like 5 times as long, and a lot more typing.

 

Yeah, but now, anywhere you need a customers details all you need call is....

 

<?php

  include "customer.class.php";
  $myCustomer2 = new Customer(121);

?>

[JustinK101]

Ok, so I guess that is nice, but whats the trick to creating a new customer, or updating a customer? Is there such things at GET and SETS like in C#? Also, if I made a class for Order, does Order extend Customer, or inherit the Customer class?

 

I guess I don't quite fully understand how I can make a customer class which allows, retrieving, creating, updating, and deleting of data via a MySQL database.

 

Also in my current class a Customer is only one, how would I pull all customers? Like I want a list of all customers?

[emehrkay]

here is how i designed my personal db class

 

i have a parent db class that handles all of the db interaction, then i have classes for each table in the db with static methods that contain prepaired statements to run queries

 

class db{

//connects to the db, handles queries etc, also a singleton

}

 

class user extends db{

public static function insert($name, $pass){

//insert query

$this->runquery($query); //runquery() is in db

}

}

 

and i use it like

 

require 'user.sql.php';

$add_user = user::insert($name, $pass);

 

thats just one of a billion ways to handle it, and it works well for me

[JustinK101]

here is how i designed my personal db class

 

i have a parent db class that handles all of the db interaction, then i have classes for each table in the db with static methods that contain prepaired statements to run queries

 

class db{

//connects to the db, handles queries etc, also a singleton

}

 

class user extends db{

public static function insert($name, $pass){

//insert query

$this->runquery($query); //runquery() is in db

}

}

 

and i use it like

 

require 'user.sql.php';

$add_user = user::insert($name, $pass);

 

thats just one of a billion ways to handle it, and it works well for me

 

Could you provide more of the code? Not sure I follow that. One thing I want to do, is give me flexability to add and remove columns from a table without making a lot of changes all over the place.

[emehrkay]

Im not sure that i understand what you want - you want to modify tables without messing up queries that were already written that may contain those columns?

[redbullmarky]

you could do worse than reading up a bit more on Active Record: http://en.wikipedia.org/wiki/Active_record . I actually use an implementation based on CakePHP (which in turn is based on Rails), so I can just do stuff like:

 

<?php
// simple example to read user with 'id' of 3, change its username and change it back.
// pointless exercise but just an example of what can be done....
$user = new User(); // user class extends model class

$user->id = 3;
$user->read(); // SELECT query: SELECT * FROM users WHERE id = 3

$oldusername = $user->username;

$user->username = 'hello';
$id = $user->save(); // UPDATE or INSERT query depending if 'id' field is set in my object

// UPDATE users SET username = '$oldusername' WHERE id = 3
$user->saveField('username', $oldusername); 
?>

 

the point really, as thorpe suggested, is that I dont need to keep rewriting common queries, or even escaping data for queries. my methods automatically run inputted data through mysql_real_escape_string and built the queries for me. Consider if I create a registration page. My User model can be used again and again on many sites, even if my table structure alters, with minimal changes rather than rewriting entire queries. I also dont need to check whether to use INSERT or UPDATE when saving data. I can also change the DB to something like MSSQL, Oracle, etc without breaking my main code. Hell, I can even use flat file DB if I want, yet my code remains the same.

 

PHP does have __get , __set and __call magic methods should you need them, which you can see at work in my example where i use $user->username and $user->id . See here

 

Hope that helps!

Cheers