The visibility of a property or method can be defined by prefixing the
declaration with the keywords: public, protected or private. Public
declared items can be accessed everywhere. Protected limits access to
inherited classes (and to the class that defines the item). Private limits
visibility only to the class that defines the item.
Class members must be defined with public, private, or protected.
Example 18-7. Member declaration
<?php
class MyClass {
public $public = "MyClass::public!\n";
protected $protected = "MyClass::Protected!\n";
protected $protected2 = "MyClass::Protected2!\n";
private $private = "MyClass::private!\n";
function printHello() {
print "MyClass::printHello() " . $this->private;
print "MyClass::printHello() " . $this->protected;
print "MyClass::printHello() " . $this->protected2;
}
}
class MyClass2 extends MyClass {
protected $protected = "MyClass2::protected!\n";
function printHello() {
MyClass::printHello();
print "MyClass2::printHello() " . $this->public;
print "MyClass2::printHello() " . $this->protected;
print "MyClass2::printHello() " . $this->protected2;
/* Will result in a Fatal Error: */
//print "MyClass2::printHello() " . $this->private; /* Fatal Error */
}
}
$obj = new MyClass();
print "Main:: " . $obj->public;
//print $obj->private; /* Fatal Error */
//print $obj->protected; /* Fatal Error */
//print $obj->protected2; /* Fatal Error */
$obj->printHello(); /* Should print */
$obj2 = new MyClass2();
print "Main:: " . $obj2->private; /* Undefined */
//print $obj2->protected; /* Fatal Error */
//print $obj2->protected2; /* Fatal Error */
$obj2->printHello();
?>
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Note:
The use PHP 4 use of declaring a variable with the keyword 'var' is
no longer valid for PHP 5 objects. For compatibility a variable declared
in php will be assumed with public visibility, and a
E_STRICT warning will be issued.