The Basicsclass
Every class definition begins with the keyword class, followed by a class
name, which can be any name that isn't a reserved
word in PHP. Followed by a pair of curly braces,
which contains the definition of the classes members and methods. A
pseudo-variable, $this is available when a method is
called from within an object context. $this is a
reference to the calling object (usually the object to which the method
belongs, but can be another object, if the method is called
statically from the context
of a secondary object). This is illustrated in the following examples:
<varname>$this</varname> variable in object-oriented language
foo();
A::foo();
$b = new B();
$b->bar();
B::bar();
?>
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&example.outputs;
Simple Class definition
var;
}
}
?>
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The default value must be a constant expression, not (for example) a
variable, a class member or a function call.
Class members' default value
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There are some nice functions to handle classes and objects. You might want
to take a look at the Class/Object
Functions.
new
To create an instance of a class, a new object must be created and
assigned to a variable. An object will always be assigned when
creating a new object unless the object has a
constructor defined that throws an
exception on error. Classes
should be defined before instantiation (and in some cases this is a
requirement).
Creating an instance
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When assigning an already created instance of a class to a new variable, the new variable
will access the same instance as the object that was assigned. This
behaviour is the same when passing instances to a function. A copy
of an already created object can be made by
cloning it.
Object Assignment
var = '$assigned will have this value';
$instance = null; // $instance and $reference become null
var_dump($instance);
var_dump($reference);
var_dump($assigned);
?>
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&example.outputs;
string(30) "$assigned will have this value"
}
]]>
extends
A class can inherit methods and members of another class by using the
extends keyword in the declaration. It is not possible to extend multiple
classes, a class can only inherit one base class.
The inherited methods and members can be overridden, unless the parent
class has defined a method as final,
by redeclaring them within the same name defined in the parent class.
It is possible to access the overrided method or members by
referencing them with parent::
Simple Class Inherintance
displayVar();
?>
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&example.outputs;