Code descriptions for PHP classes and objects

1. Define and create classes and objects:

Define classes to use the class keyword. Example: Class Name {//attribute and method}

Create objects using the New keyword. For example: $p 1 = new class name, you can create multiple objects based on one class.

2. Class Property values

(1) In a class, in addition to declaring properties, you can assign a value to a property, but only specify a constant value for the property in the following ways:

Example 1: public    $last _visitor = ' Donnan ';    Correct public    $last _visitor = 9;    Correct public    $last _visitor = Array (' Jesse ');    Correct public    $last _visitor = Pick_visitor ();    Error public    $last _visitor = ' Chris '. ' 9 ';    Error (2) The method in the class specifies a very magnitude for the variable:    Example 2:

  Class guest_book{public        $last _visitor;        Public Function Update ($comment, $visitor) {            if (!empty ($comments)) {                Array_unshift ($this->comments, $ Comments);                $this->last_visitor = $visitor;    A method in a class specifies a very important value for a variable}}}    

　　

(3) Specify a value for the variable in the process of creating the object, which is assigned in the constructor of the class. A constructor refers to a method that is called automatically when a new object is created, with the name __construct () example 3:class guset_book{public $comments; public $last _visitor; function __consturct ($user) {$dbh = Mysqli_connect (' localhost ', ' username ', ' password ', ' site '); $user = Mysqli_real_ Escape_string ($DBH, $user); $sql = "Select comments, last_visitor from guest_book where user = ' $user '"; $r = Mysqli_query ($DBH, $sql); if ($obj = Mysqli_fetch_object ($DBH, $r)) {$this->comments = $obj->comments;//Specify a very magnitude for the variable $this->last_visitor = $ obj->last_visitor; Specify a value for the variable}}} $GB = new Guest_book (' Stewart '); Specify a value for a variable
http://www.cnblogs.com/sosoft/
3. Inheritance and coverage
(1) by inheriting to extend an existing class, use the keyword extends:

Class class name extends parent class name {} (2) overrides the parent class method:    Example 4:

Class db{    function GetResult () {        return $this->result;    }    function query ($sql) {        error_log ("Queryy () must Bue overridden by a database-specific child");        return false;    }} Class MySQL extends db{/////    MySQL class inherits the GetResult () method from the parent class DB, but re-implements its own specific MySQL method query ()    function query ($ SQL) {           $this->result = mysql_query ($sql);}    }

　　

(3) Precede the method name with Parent:: A method to explicitly invoke a parent class: Example 5:fuction Escape ($sql) {$safe _sql = mysql_real_escape_string ($sql); $safe _sql = Parent::escape ($safe _sql); The parent method adds ' around $DQL; return $safe _sql; } (4) Note: When a method in a subclass overrides a method in the parent class, the parent class's method is not automatically called unless explicitly referenced (parent::).

Code descriptions for PHP classes and objects