CompatibilityCode:Wikka

Revision [16673]

This is an old revision of CompatibilityCode made by EvtOux on 2007-05-31 10:34:50.

Compatibility Code

Different types of compatibility code

Compatibility code can be classified into three kinds, depending on what kind of differences we are hiding; the aim is always to hide the complexity of working around differences from calling code that needs the functionality:

Classification

Missing functions

Code to compensate for PHP functions that may be missing in older versions; this allows (almost) equivalent functionality when Wikka is running on an older PHP version

Code to compensate for PHP MySQL functions that may be be available only for a newer MySQL version than is installed; this allows for (almost) equivalent functionality when Wikka is using an older MySQL version

Hiding decision logic

Code that decides which of two possible functions or methods to call depending on PHP or MySQL version installed; by wrapping such decision logic in a single method, the version-dependent decision logic can be hidden with single API

Configuration

Code that compensates for differences in PHP configuration that may not be under the control of the WikiAdmin or may not be to changed in order not to break other PHP applications.

Compatibility code in Wikka 1.1.6.0

Wikka 1.1.6.0 already has some compatibility code in place, but it could do better... See below for some (proposed) new additions.

`mysql_real_escape_string()`

Classification

Missing function.

Code

The function mysql_real_escape_string() is available in PHP as of version 4.3; Wikka specifies PHP 4.1.0 as minimum PHP version so we need to provide a (near) equivalent for this.

The code is found near the start of wikka.php:

if ( ! function_exists("mysql_real_escape_string") )
{
function mysql_real_escape_string($string)
{
return mysql_escape_string($string);
}
}

This clearly shows the basic pattern for "missing function" compatibility code:

check whether a function of that name exists

if not, define a function with the same name and as much as possible the same interface

in the function body imitate as much as possible the functionality of the missing function

This ensures that the intended function can be called as normal: if the function does not exist in the current installation, the compatibility code will kick in.

Note that mysql_escape_string() is not exactly equivalent with mysql_real_escape_string(); possibly the code here could be extended a bit to provide better compaitibilty.

`Magic quotes`

Classification

Configuration

Code

PHP may be configured to use "magic quotes". When magic_quotes are on, all ' (single-quote), " (double quote), \ (backslash) and NUL's are escaped with a backslash automatically for GPC (Get/Post/Cookie) operations. To avoid having to check for these backslashes in every string we get via cookies or POST and GET requests the following code turns off magic quotes and removes them where found, so any further code does not have to deal with them. The code is (currently) found near the end of wikka.php:
%%(php;1029) workaround for the amazingly annoying magic quotes.
function magicQuotesSuck(

Wikka : CompatibilityCode

Revision [16673]