Object Oriented Programming in PHP

List of Items of Interest What is a Class What is an Object What is a Singleton Multiple Objects, How to store. Advantages and Disadvantages of OOP Parts of a Class – Properties – Methods – Constructors Creating an Object Passing data to an object when it is first created or to the constructor Passing data to a property Passing data to a method Getting data from a property Getting data from a method Naming issues/requirements Printing PDO vs mysql_link Sending multiple variables of data back from a method Parsing of the returned data

What is a Class A Class is a template of code that is used to create an Object. Objects do the work, Classes are the design of the code to do the work.

What is an Object An Object is a Instantiation of a Class. If you have only one Object from a class it is called a Singleton If you have multiple Objects from a class it is best to store the objects in an array.

Advantages and Disadvantages of OOP If you have a large project in PHP or if you have a project that is in a constant state that it is running (other then PHP) then you should use OOP. If you have a small project that does not use a lot of reused code then Procedural programming is better as it is lighter.

Parts of a Class Properties – If you have variables that are to be shared between methods it is best to declare them as properties. – As of PHP5 properties start with private, public or protected – The visibility of private, public or protected is different then ActionScript – public $name = “Doug”; – They are reference with $this->name in methods – They are references from the main file with $oObject->name ;

Parts of a Class Methods – Methods are functions that work on data. – As of PHP5 methods start with private, public or protected – The visibility of private, public or protected is different then ActionScript – public function myToDo () { } – They are reference with $this->myToDo () in other methods – They are referenced from the main file with $oObject->myToDo () ;

Parts of a Class Constructors – Constructors are special methods that are called when an Object is created. – As of PHP5 Constructors are named as __construct() – The visibility of private, public or protected is different then ActionScript – public function __construct () { } – I usually use the constructor to set default properties for the object such as connecting to the Database.

Creating an Object You first need to include the Class with a require_once to reference the file the class is in. I always start the name of my objects with a lowercase o and then camel case the rest of the name. $oObject Use the new command to create the object $oObject = New Bicycles();

Passing data to an object when it is first created or to the constructor When creating the object from the class pass variable data in the brackets to the constructor. $oObject = New Bicycles($id); Class Bicycles { public $id = “”; public function __construct ($id) { $this->id = $id; }

Passing data to a property $oObject->id = $id; // outside object $oObject->id = “22”; // outside object $this->id = $id; // from within object $this->id = “22”; // from within object

Passing data to a method Data id passed in the brackets of the method name; $oObject->getBicycle($id); // outside object $oObject->getBicycle(“22”); // outside object $this->getBicycle($id); // from within object $this->getBicycle(“22”); // from within object

Getting data from a property $id = $oObject->id ; // outside object print $oObject->id ; // outside object $id= $this->id; // Do not do this as you just need to reference the property only from within object

Getting data from a method $title = $oObject->getBicycleTitle($id); // outside object print $oObject->getBicycleTitle($id); // outside object $title = $this->getBicycleTitle($id); // from within object (Never Print from with in a Method except for debugging)

Naming issues/requirements When naming properties and methods use camel case When naming variables use lowercase with underscores. The use of objects reduces name space issues Start all class names with a capital Start all objects with a lower case o

Printing NEVER use print or echo with a class or object (printing can only be used for debugging) It is bad form data does not print where it needs to be seen.

PDO vs mysql_link The procedural way of connecting to a database is to create a resource link such as $mysql_link For OOP use the PDO way which is PHP Database Objects Create a property in the __construct that has the reference to the PDO. public $pDbh ; // define constructor public function __construct() { require_once("connect_dbh.php"); $this->pDbh = &$dbh; }

PDO vs mysql_link connect_dbh.php <?php try { $user = ”youraccount"; $pass = ”yourpassowrd"; $dbh = new PDO('mysql:host=localhost;dbname=yourdatabase', $user, $pass); } catch (PDOException $e) { print("Error: ".$e->getMessage()." "); } ?>

PDO vs mysql_link SELECT $query = "SELECT title FROM bicycles WHERE id = '$id'"; foreach ($this->pDbh->query($query) as $row) { $title = stripslashes($row[0]); }

PDO vs mysql_link INSERT, DELETE or UPDATE $query = ”UPDATE bicycles SET title = ‘$title’ WHERE id = '$id'"; $this->pDbh2->query($query);

Sending multiple variables of data back from a method You can use a return command to send a single variable back from the calling method. public function addThis ($a,$b) { $total = $a + $b; return $total; }

Sending multiple variables of data back from a method To send multiple variables back in a return you need to place the variables into an array. public function getBicyclesList () { $data = “”; $query = "SELECT id, title FROM bicycles ORDER BY id ”; $x = 0; foreach ($this->pDbh->query($query) as $row) { $id= stripslashes($row[0]); $title = stripslashes($row[1]); $data[$x][‘id’] = $id; $data[$x][‘title’] = $title; ++$x; } return $data; }

Parsing of the returned data If the data is a simple structure then just print it or place into a variable. print $oObject->addThis(12, 6) ; // prints 18

Parsing of the returned data If the data is an array structure then you need to parse the array. $bikeListArray = $oBicycles->getBicyclesList(); foreach ($bikeListArray as $key=>$bike) { $id = $bike[‘id’]; $title = $bike[‘title’]; print(“ $title ”); }

File Names Each class resides in it’s own file Each file has the name class in it. The file begins with the name of the class bicycles.class.php These files will reside in the inc/php folder