PHP: Backward Incompatible Changes

Last updated: Fri, 10 Oct 2008

Backward Incompatible Changes

Although most existing PHP 4 code should work without changes, you should pay attention to the following backward incompatible changes:

There are some new reserved keywords.
strrpos() and strripos() now use the entire string as a needle.
Illegal use of string offsets causes E_ERROR instead of E_WARNING. An example illegal use is: $str = 'abc'; unset($str[0]);.
array_merge() was changed to accept only arrays. If a non-array variable is passed, a E_WARNING will be thrown for every such parameter. Be careful because your code may start emitting E_WARNING out of the blue.
PATH_TRANSLATED server variable is no longer set implicitly under Apache2 SAPI in contrast to the situation in PHP 4, where it is set to the same value as the SCRIPT_FILENAME server variable when it is not populated by Apache. This change was made to comply with the » CGI specification. Please refer to » bug #23610 for further information, and see also the $_SERVER['PATH_TRANSLATED'] description in the manual. This issue also affects PHP versions >= 4.3.2.
The T_ML_COMMENT constant is no longer defined by the Tokenizer extension. If error_reporting is set to E_ALL, PHP will generate a notice. Although the T_ML_COMMENT was never used at all, it was defined in PHP 4. In both PHP 4 and PHP 5 // and /* */ are resolved as the T_COMMENT constant. However the PHPDoc style comments /** */, which starting PHP 5 are parsed by PHP, are recognized as T_DOC_COMMENT.
$_SERVER should be populated with argc and argv if variables_order includes "S". If you have specifically configured your system to not create $_SERVER, then of course it shouldn't be there. The change was to always make argc and argv available in the CLI version regardless of the variables_order setting. As in, the CLI version will now always populate the global $argc and $argv variables.
An object with no properties is no longer considered "empty".
In some cases classes must be declared before use. It only happens if some of the new features of PHP 5 (such as interfaces) are used. Otherwise the behaviour is the old.
get_class(), get_parent_class() and get_class_methods() now return the name of the classes/methods as they were declared (case-sensitive) which may lead to problems in older scripts that rely on the previous behaviour (the class/method name was always returned lowercased). A possible solution is to search for those functions in all your scripts and use strtolower(). This case sensitivity change also applies to the magical predefined constants __CLASS__, __METHOD__, and __FUNCTION__. The values are returned exactly as they're declared (case-sensitive).
ip2long() now returns FALSE when an invalid IP address is passed as argument to the function, and no longer -1.
If there are functions defined in the included file, they can be used in the main file independent if they are before return() or after. If the file is included twice, PHP 5 issues fatal error because functions were already declared, while PHP 4 doesn't complain about it. It is recommended to use include_once() instead of checking if the file was already included and conditionally return inside the included file.
include_once() and require_once() first normalize the path of included file on Windows so that including A.php and a.php include the file just once.

Example #1 strrpos() and strripos() now use the entire string as a needle


<?php
var_dump(strrpos('ABCDEF','DEF')); //int(3)

var_dump(strrpos('ABCDEF','DAF')); //bool(false)
?>

Example #2 An object with no properties is no longer considered "empty"


<?php
class test { }
$t = new test();

var_dump(empty($t)); // echo bool(false)

if ($t) {
    // Will be executed
}
?>

Example #3 In some cases classes must be declared before used


<?php

//works with no errors:
$a = new a();
class a {
}


//throws an error:
$a = new b();

interface c{
}
class b implements c {
} 

?>

CLI and CGI

Migrating from PHP 4 to PHP 5.0.x

Last updated: Fri, 10 Oct 2008

add a note User Contributed Notes
Backward Incompatible Changes

paul at oconnor-web dot net
10-Apr-2008 09:17


The __call function will also lowercase the method arguement:





<?php


   function __call($method, $args) {


     if ($method == 'Foo') {


       return true;


     } else {


       return false


     }


   }


?>





(= false)

Steven
20-Mar-2008 11:07


Three more that we discovered:





== 1. No longer can re-assign $this ==





The follwoing example works under PHP4 (it outputs "OK"), but produces a fatal error under PHP5: 





<?php


  class a 


  { 


    var $text;


    function a() { $this->text = 'OK'; }


  }





  class b


  {


    var $text = 'NOT OK';


    function b() { $this = new a(); }


  }


    


  $myClass = new b();


  echo $myClass->text;


?>





== 2. No comments allowed after shorthand echo block ==





The follwoing example works under PHP4, but produces a sytax error under PHP5.





<?=//comment?>





== 3. Constructors return a reference as default ==





The follwoing example works under PHP4, but produces an E_NOTICE notice under PHP5.





<?php


  class MyClass { function MyClass() { echo('OK'); } }


  $myObj = null;


  $myObj &= new MyClass();


?>





Removing the ampersand solves the problem

Aggelos Orfanakos
09-Nov-2007 12:10


As with array_merge(), array_merge_recursive() returns NULL in PHP 5 if a non-array parameter is passed to it.

Sinured
10-Aug-2007 09:43


Not mentioned above: The PHP/FI 2 function style (old_function aka cfunction) is no longer supported as of PHP 5.

nami
27-Jul-2007 12:22


addition of the note on 07-Sep-2004 06:40





if you write down your code like this PHP5 will just work fine:





<?php


     $array_1 = array('key1'=>'oranges','key2'=>'apples');


     $array_2 = array('key3'=>'pears','key4'=>'tomatoes');


     $array_3 = array();


     $arr_gemerged = array_merge($array_1,$array_2,$array_3);


     echo "result:<br>";


     print_r($arr_gemerged);


     echo "<br>";


?>





---





so you have to declare array_3 as array() instead of NULL

kemal djakman
22-Jun-2007 11:11


The handling of accessing empty property of a class error has also changed:

<?php



class Foo {



    var $Bar = 'xxx';



    function F() {

        echo $this->$Bar;

    }

}



$Obj = new Foo();

$Obj->F();



?>



Notice the $ sign after object dereference opr?  $Bar is empty inside method F.   PHP4 would only generate a warning, PHP5 throws a fatal error

Amir Laher
30-Apr-2007 07:34


Some other things to be aware of:



some extra strictness:

* object members can no longer be accessed using array-member syntax

* function-calls with too many arguments will now cause errors.



Also, from PHP5.2, custom session handlers are affected:

* Best not to use global objects in custom session-handling functions. These would get destructed *before* the session is written (unless session_write_close() is called explicitly).

01-Mar-2006 09:03


is_a have been deprecated. You can simply replace all occurences with the new instanceOf operator, although this will break backwards-compatibility with php4.

dward . maidencreek.com
02-Nov-2004 07:54


Another change that we've had problems with while trying to use PHP4 code in PHP5 is how $this is carried across static method calls if they are not declared static in PHP5.  The main issue was that debug_backtrace() now shows the first class with -> instead of the second with :: in the backtrace element when the method in the second class was called statically (using ::) from a method in the first class.

08-Sep-2004 02:40


Be careful with array_merge in PHP5.1 not only a E_WARNING is thrown, but also the result is an empty array. So if you merge two select queries and the last one is empty you will end up with no array at all.





<?php


        $array_1 = array('key1'=>'oranges','key2'=>'apples');


        $array_2 = array('key3'=>'pears','key4'=>'tomatoes');


        $array_3 = null;


        $arr_gemerged = array_merge($array_1,$array_2,$array_3);


        print_r($arr_gemerged);


        echo "<br>";


?>





Result on php4:


Array ( [key1] => oranges [key2] => apples [key3] => pears [key4] => tomatoes )





Result on php5:


Warning: array_merge() [function.array-merge]: Argument #3 is not an array in /removed/by/danbrown/for/manual.php on line 7

john.g
27-Aug-2004 03:45


PATH_TRANSLATED is handy when using Apache's ModRewrite engine, as it gives you the name and path of the resulting file rather than the one that was requested by the user. Since PHP 5.0 and Apache 2 no longer support this variable, I created a workaround by adding an environment variable to my ModRewrite command:



Original:

RewriteRule ^/test/(.*)\.php(.*) /test/prefix_$1.php$2



Adjusted:

RewriteRule ^/test/(.*)\.php(.*) /test/prefix_$1.php$2 [E=TARGET:prefix_$1.php]



I could then find out the resulting file name through the super global $_ENV, for instance:



<?php

echo "The actual filename is ".$_ENV['REDIRECT_TARGET'];

?>



Note: The "REDIRECT_" prefix appears to be allocated automatically by ModRewrite.

cyberhorse
06-Aug-2004 03:07


clone() is a php function now.



if you create a subclass, it no longer uses samename methods in superclass as a constructor.

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CLI and CGI

Migrating from PHP 4 to PHP 5.0.x

Last updated: Fri, 10 Oct 2008