PHP Manual
后退附录 B. Migrating from PHP 4 to PHP 5前进


Backward Incompatible Changes

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

  • strrpos() and strripos() now use the entire string as a needle.

  • Illegal use of string offsets causes E_ERROR instead of E_WARNING.

  • 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.

  • The T_ML_CONSTANT 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_CONSTANT 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 used. It only happens only if some of the new features of PHP 5 are used. Otherwise the behaviour is the old.

  • get_class() starting PHP 5 returns the name of the class as it was declared which may lead to problems in older scripts that rely on the previous behaviour (the class name was lowercased). A possible solution is to search for get_class() in all your scripts and use strtolower().

  • ip2long() now returns FALSE when an invalid IP address is passed as argument to the function, and no longer -1.

例子 B-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)
?>

例子 B-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
}
?>

例子 B-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 {
}

?>



后退起点前进
Migrating from PHP 4 to PHP 5上一级CLI and CGI