Object Oriented Programming in PHP

1. Object Oriented Programming in PHP

2. 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 vsmysql_link • Sending multiple variables of data back from a method • Parsing of the returned data

3. 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.

4. 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.

5. 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.

6. 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 ;

7. 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 () ;

8. 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.

9. 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();

10. 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; } }

11. 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

12. 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

13. 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

14. 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)

15. 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

16. 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.

17. PDO vsmysql_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; }

18. PDO vsmysql_linkconnect_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()."<br /> "); } ?>

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

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

21. 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; }

22. 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; }

23. 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

24. 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 = $bike[‘title’]; print(“<option value=\”$id\”>$title</option>”); }

25. 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