This post is archived and probably outdated.

Improvements for PHP application portability in

2011-07-25 22:44:00

I was writing about before, many things improved there meanwhile. Most notably we have a committed version number: The next PHP release will be called PHP 5.4. The topic I want to talk about today is "Improved application portability" which covers multiple small changes which aim at making it simpler for developers to write applications working on any PHP setup.

Separating <?= from short_open_tags

PHP knows quite a few ways to separate PHP code from surrounding text (usually HTML), most applications use <?php as that works on every system. There is a short form of this, <?, which can be disabled using php.ini's short_open_tags setting. Being able to disable this is important when embedding PHP code into XML documents containing XML processing instructions. Now we also have <?= which, basically, is a shortcut for <?php echo. This tag is useful when using PHP as templating language as it prevents cluttered code. The issue in current version of PHP is that this is bound to short_open_tags, so portable applications can't rely on it. But PHP 5.4 will bring the solution: <?= will always be there, independently from short_open_tags. Yay!

No more magic_quotes

In the old times it was easy to write code using PHP.

$q = mysql_query("SELECT * FROM t WHERE name = '$name' ");

And you had, thanks to register_globals, some data to work on and this was mostly secure as PHP automatically escaped request data. But well this escaping worked only in a few cases acceptable good. Besides not knowing anything about other encodings or DBMS-specific escape sequences it also failed for non-string values as in

$q = mysql_query("SELECT * FROM t WHERE id = $id ");

Where the external value wasn't escaped. So portable applications, which aim at being secure nowadays have to check whether magic_quote_gpc is enabled, then remove the "bad" quotes and then finally escape again using the appropriate way. That's quite  an annoyance and doing this the wrong way can cause bad bugs (like forcing such a replacement logic in an endless recursion by providing arrays) So nobody really likes magic_quotes. So with PHP 5.4 they are gone. No more need to worry about them. Use the proper escaping and you're done. Wonderful. Only issue: Legacy applications might rely on magic_quotes so when upgrading PHP make sure the application does the required escaping itself so almost-secure applications won't become insecure.

Dropped explicit --enable-zend-multibyte compile-time option

Especially in Asia people use multi-byte encodings which aren't ASCII-compatible so mixing them with PHP code might be hard. In current versions of PHP there is a compile-time option to enable a special multibyte mode for the engine which will handle this in the engine so PHP code can be provided using these encodings. By this portable applications had a hard time due to this conversion (not) being done. Thanks to the work by Dmitry and Moriyoshi this mode is now always enabled whithout penalty for people not depending on it and the extended functionality from mbstring can be provided as a shared module. By this distributors can provide a single build which will work for everybody.

Closing remarks

As always in this series: Be aware that things discussed here might change. Please try out the current snapshot of PHP 5.4 and test it with your applications. No we can still fix backwards compatibility breaks. fixing them after a release will possibly break it for people depending on the new behavior. Happy coding!