Migration51/oop-Phpdoc专题
Class and object changes
instanceof, is_a(), is_subclass_of() and catch
In PHP 5.0, is_a() was deprecated and replaced by the instanceof
operator. There were some issues with the initial implementation of
instanceof, which relied on __autoload() to search for missing
classes. If the class was not present, instanceof would throw a fatal
E_ERROR
due to the failure of __autoload() to discover that
class. The same behaviour occurred in the catch operator and the
is_subclass_of() function, for the same reason.
None of these functions or operators call __autoload() in PHP 5.1.x, and the class_exists() workarounds used in code written for PHP 5.0.x, while not problematic in any way, are no longer necessary.
Abstract private methods
Abstract private methods were supported between PHP 5.0.0 and PHP 5.0.4, but were then disallowed on the grounds that the behaviours of private and abstract are mutually exclusive.
Access modifiers in interfaces
Under PHP 5.0, function declarations in interfaces were treated in
exactly the same way as function declarations in classes. This has not
been the case since October 2004, at which point only the public
access modifier was allowed in interface function declarations. Since
April 2005 - which pre-dates the PHP 5.0b1 release - the static
modifier has also been allowed. However, the protected and private
modifiers will now throw an E_ERROR
, as will abstract. Note that
this change should not affect your existing code, as none of these
modifiers makes sense in the context of interfaces anyway.
Changes in inheritance rules
Under PHP 5.0, it was possible to have a function declaration in a derived class that did not match the declaration of the same function in the base class, e.g.
This code will cause an E_STRICT
error to be emitted under PHP
5.1.x.
<?php
class Base {
function &return_by_ref() {
$r = 1;
return $r;
}
}
class Derived extends Base {
function return_by_ref() {
return 1;
}
}
?>
Class constants
Under PHP 5.0.x, the following code was valid:
Under PHP 5.1.x, redefinition of a class constant will throw a fatal
E_ERROR
.
<?php
class test {
const foobar = 'foo';
const foobar = 'bar';
}
?>