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PHP - Constructors
I know this is a PHP site, but is it true that in Java the constructor has the same name as the class name?
I went to the PHP.net manual and it has a similar set up. Is that correct? I thought there was some other convention that differed from Java? TomTees Similar TutorialsI am working with the Zend Framework and I noticed that some of the classes do not have constructor. For instance, Zend_ACL does not have a constructor. What happens with this class is instantiated? Is it just a sort of empty object? The class does not extend another class so a parent constructor is not being called. I'm doing some basic object coding to get my head around OOP PHP, but I've come across something I can't get to work. I've got two identical peices of code, MyClass is defined, MyClass2 is then defined as an extension of MyClass. MyClass has three properties Public, Private and Protected. In my first example I can access Public and Protected via a method in MyClass2, this class does NOT have a constructor. The second example has a constructor but I cannot access Public: Code: [Select] <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> <html> <body> <?php ECHO "MyClass2 does not have a constructor, Public & Protected both echo correctly from MyClass2->printHello!!!<BR>"; /** * Define MyClass */ class MyClass { public $public; protected $protected; private $private; protected $varXXX; function __construct() { $this->public = "Public"; $this->protected = "Protected"; $this->private = "Private"; //$this->printHello(); } function printHello() { echo $this->public . "!!!<BR>"; echo $this->protected . "!!!<BR>"; echo $this->private . "!!!<BR>"; } } /** * Define MyClass2 */ class MyClass2 extends MyClass { // We can redeclare the public and protected method, but not private protected $protected = 'Protected2'; /* function __construct() { echo $this->public . "#<BR>"; echo $this->protected . "#<BR><BR>"; //echo $this->private . "???<BR>"; } */ function printHello() { echo $this->public . "???<BR>"; echo $this->protected . "???<BR><BR>"; //echo $this->private . "???<BR>"; } } $obj = new MyClass(); //echo $obj->public . "<BR>"; // Works //echo $obj->protected; // Fatal Error //echo $obj->private; // Fatal Error //$obj->printHello(); // Shows Public, Protected and Private $obj2 = new MyClass2(); //echo $obj2->public; // Works //echo $obj2->private; // Undefined //echo $obj2->protected; // Fatal Error $obj2->printHello(); // Shows Public, Protected2, Undefined ?> </body> </html> RESULTS IN: Public??? Protected??? Code: [Select] <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> <html> <body> <?php ECHO "MyClass2 DOES have a constructor, Public does not work from MyClass2->printHello!!!<BR>"; /** * Define MyClass */ class MyClass { public $public; protected $protected; private $private; protected $varXXX; function __construct() { $this->public = "Public"; $this->protected = "Protected"; $this->private = "Private"; //$this->printHello(); } function printHello() { echo $this->public . "!!!<BR>"; echo $this->protected . "!!!<BR>"; echo $this->private . "!!!<BR>"; } } /** * Define MyClass2 */ class MyClass2 extends MyClass { // We can redeclare the public and protected method, but not private protected $protected = 'Protected2'; function __construct() { echo $this->public . "#<BR>"; echo $this->protected . "#<BR><BR>"; //echo $this->private . "???<BR>"; } function printHello() { echo $this->public . "???<BR>"; echo $this->protected . "???<BR><BR>"; //echo $this->private . "???<BR>"; } } $obj = new MyClass(); //echo $obj->public . "<BR>"; // Works //echo $obj->protected; // Fatal Error //echo $obj->private; // Fatal Error //$obj->printHello(); // Shows Public, Protected and Private $obj2 = new MyClass2(); //echo $obj2->public; // Works //echo $obj2->private; // Undefined //echo $obj2->protected; // Fatal Error $obj2->printHello(); // Shows Public, Protected2, Undefined ?> </body> </html> RESULTS IN: # << Missing the property's contents Protected2# ??? << Missing the property's contents Protected2??? Any ideas why I cannot access the property's contents in the second example when the only difference is that it has a constructor? |
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