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PHP Version Compatability

Thu, 8th January, 2009 - Posted by Administration

Any discussion on the subject of PHP Version Compatability would be incomplete if no mention was made about older versions of PHP and the php.ini settings register_globals and register_long_arrays. These two settings alone seem to create hours of frustation for PHP Web designers and people trying to move their web site from one provider to another.

register_globals

As of PHP 5 the php.ini setting “register_globals” has a default setting of “off.” Providers continue to support it to reduce tech support calls. Web Devlopers continue to use it because they can. It has been depreciated and turned off for a reason, Security! If your ISP allows your web devloper to use super Globals they will continue to do so out of habit or ignorence.

It looks like this in the php.ini file
register_globals = off;

When this setting is set to “on,” all variables in a php script can be accessed without having to use super global arrays. This basically means that it does not matter how you send your variables. If you send variable — first_name — to script “b.php” using method POST, you will not have to use the familiar $_POST['first_name'] to get at the value you assigned to it. All you will have to do is type your variable — $first_name.

At first, this seems like the easier and more logical choice since it obviously requires the coder to type less code. This practice was abandoned due to serious security risks. Quoting from the php.ini file “You should do your best to write your scripts so that they do not require register_globals to be on. Using form variables as globals can easily lead to possible security problems, if the code is not very well thought of.” The full implications of that statement is beyond the scope of this web page. Writing code with register_globals on is usually not a good idea.

register_long_arrays

register_long_arrays is also turned off by default in php5. The only reason to turn this setting to “on,” would be to run older code on newer versions of PHP. Older PHP versions used “HTTP_GET_VARS” instead of code like “$_GET[''].”

PHP is already popular, used in millions of domains (according to Netcraft), supported by most ISPs and used by household-name Web companies like Yahoo! The upcoming versions of PHP aim to add to this success by introducing new features that make PHP more usable in some cases and more secure in others. Are you ready for PHP V6? If you were upgrading tomorrow, would your scripts execute just fine or would you have work to do? This article focuses on the changes for PHP V6 — some of them back-ported to versions PHP V5.x — that could require some tweaks to your current scripts.

If you’re not using PHP yet and have been thinking about it, take a look at its latest features. These features, from Unicode to core support for XML, make it even easier for you to write feature-filled PHP applications.

New PHP V6 features

PHP V6 is currently available as a developer snapshot, so you can download and try out many of the features and changes listed in this article. For features that have been implemented in the current snapshot, see Resources.

Improved Unicode support

Much improved for PHP V6 is support for Unicode strings in many of the core functions. This new feature has a big impact because it will allow PHP to support a broader set of characters for international support. So, if you’re a developer or architect using a different language, such as the Java™ programming language, because it has better internationalization (i18n) support than PHP, it’ll be time to take another look at PHP when the support improves.

Because you can download and use a developer’s version of PHP V6 today, you will see some functions already supporting Unicode strings. For a list of functions that have been tested and verified to handle Unicode, see Resources.

What is Unicode?

Unicode is an industry-standard set of characters, character encoding, and encoding methodologies primarily aimed at enabling i18n and localization (i10n). The Unicode Transformation Format (UTF) specifies a way to encode characters for Unicode. For more information about Unicode and UTF, see Resources.

Namespaces

Namespaces are a way of avoiding name collisions between functions and classes without using prefixes in naming conventions that make the names of your methods and classes unreadable. So by using namespaces, you can have class names that someone else might use, but now you don’t have to worry about running into any problems. Listing 1 provides an example of a namespace in PHP.

You won’t have to update or change anything in your code because any PHP code you write that doesn’t include namespaces will run just fine. Because the namespaces feature appears to be back-ported to V5.3 of PHP, when it becomes available, you can start to introduce namespaces into your own PHP applications.

Listing 1. Example of a namespace

// I'm not sure why I would implement my own XMLWriter, but at least
// the name of this one won't collide with the one built in to PHP
namespace myNameSpace;
class XMLWriter
{
// Implementation here...
}

$writer = new myNameSpace::XMLWriter();

?>

Web 2.0 features

Depending on how you use PHP and what your scripts look like now, the language and syntax differences in PHP V6 may or may not affect you as much as the next features, which are those that directly allow you to introduce Web 2.0 features into your PHP application.

SOAP

SOAP is one of the protocols that Web services “speak” and is supported in quite a few other languages, such as the Java programming language and Microsoft® .NET. Although there are other ways to consume and expose Web services, such as Representational State Transfer (REST), SOAP remains a common way of allowing different platforms to have interoperability. In addition to SOAP modules in the PHP Extension and Application Repository (PEAR) library, a SOAP extension to PHP was introduced in V5. This extension wasn’t enabled by default, so you have to enable the extension or hope your ISP did. In addition, PEAR packages are available that allow you to build SOAP clients and servers, such as the SOAP package.

Unless you change the default, the SOAP extension will be enabled for you in V6. These extensions provide an easy way to implement SOAP clients and SOAP servers, allowing you to build PHP applications that consume and provide Web services.

If SOAP extensions are on by default, that means you won’t have to configure them in PHP. If you develop PHP applications and publish them to an ISP, you may need to check with your ISP to verify that SOAP extensions will be enabled for you when they upgrade.

XML

As of PHP V5.1, XMLReader and XMLWriter have been part of the core of PHP, which makes it easier for you to work with XML in your PHP applications. Like the SOAP extensions, this can be good news if you use SOAP or XML because PHP V6 will be a better fit for you than V4 out of the box.

The XMLWriter and XMLReader are stream-based object-oriented classes that allow you to read and write XML without having to worry about the XML details.

Things removed

In addition to having new features, PHP V6 will not have some other functions and features that have been in previous versions. Most of these things, such as register_globals and safe_mode, are widely considered “broken” in current PHP, as they may expose security risks. In an effort to clean up PHP, the functions and features listed in the next section will be removed, or deprecated, from PHP. Opponents of this removal will most likely cite issues with existing scripts breaking after ISPs or enterprises upgrade to PHP V6, but proponents of this cleanup effort will be happy that the PHP team is sewing up some holes and providing a cleaner, safer implementation.

Features that will be removed from the PHP version include:

magic_quotes
register_globals
register_long_arrays
safe_mode

Citing portability, performance, and inconvenience, the PHP documentation discourages the use of magic_quotes. It’s so discouraged that it’s being removed from PHP V6 altogether, so before upgrading to PHP V6, make sure that all your code avoids using magic_quotes. If you’re using magic_quotes to escape strings for database calls, use your database implementation’s parameterized queries, if they’re supported. If not, use your database implementation’s escape function, such as mysql_escape_string for MySQL or pg_escape_string for PostgreSQL. Listing 2 shows an example of magic_quotes use.

Listing 2. Using magic_quotes (discouraged)

// Assuming magic_quotes is on...
$sql = "INSERT INTO USERS (USERNAME) VALUES $_GET['username']";
?>

After preparing your PHP code for the new versions of PHP, your code should look like that in Listing 3.
Listing 3. Using parameterized queries (recommended)

// Using the proper parameterized query method for MySQL, as an example
$statement = $dbh->prepare(”INSERT INTO USERS (USERNAME) VALUES ?”);
$statement->execute(array($_GET['username']));
?>

Now that support for magic_quotes will be completely removed, the get_magic_quotes_gpc() function will no longer be available. This may affect some of the older PHP scripts, so before updating, make sure you fix any locations in which this functions exists.

register_globals

The register_globals configuration key was already defaulted to off in PHP V4.2, which was controversial at the time. When register_globals is turned on, it was easy to use variables that could be injected with values from HTML forms. These variables don’t really require initialization in your scripts, so it’s easy to write scripts with gaping security holes. The register_globals documentation (see Resources) provides much more information about register_globals. See Listing 4 for an example of using register_globals.

Listing 4. Using register_globals (discouraged)
// A security hole, because if register_globals is on, the value for user_authorized
// can be set by a user sending them on the query string
// (i.e., http://www.example.com/myscript.php?user_authorized=true)
if ($user_authorized) {
// Show them everyone's sensitive data...
}
?>

If your PHP code uses global variables, you should update it. If you don’t update your code to get prepared for newer versions of PHP, consider updating it for security reasons. When you’re finished, your code should look like Listing 5.

Listing 5. Being specific instead (recommended)

function is_authorized() {
if (isset($_SESSION['user'])) {
return true;
} else {
return false;
}
}

$user_authorized = is_authorized();
?>

register_long_arrays

The register_long_arrays setting, when turned on, registers the $HTTP_*_VARS predefined variables. If you’re using the longer variables, update now to use the shorter variables. This setting was introduced in PHP V5 — presumably for backward-compatibility — and the PHP folks recommend turning it off for performance reasons. Listing 6 shows an example of register_long-arrays use.

Listing 6. Using deprecated registered arrays (discouraged)
// Echo's the name of the user value given on the query string, like
// http://www.example.com/myscript.php?username=ngood
echo "Welcome, $HTTP_GET_VARS['username']!";
?>

If your PHP code looks like that shown in Listing 6, update it to look like that in Listing 7. Shut off the register_long_arrays setting if it’s on and test your scripts again.

Listing 7. Using $_GET (recommended)

// Using the supported $_GET array instead.
echo "Welcome, $_GET['username']!";
?>

safe_mode

The safe_mode configuration key, when turned on, ensures that the owner of a file being operated on matches the owner of the script that is executing. It was originally a way to attempt to handle security when operating in a shared server environment, like many ISPs would have. (For a link to a list of the functions affected by this safe_mode change, see Resources.) Your PHP code will be unaffected by this change, but it’s good to be aware of it in case you’re setting up PHP in the future or counting on safe_mode in your scripts.

PHP tags

Microsoft Active Server Pages (ASP)-style tags — the shorter version of the PHP tags — are no longer supported. To make sure this is not an issue for your scripts, verify that you aren’t using the <% or %> tags in your PHP files. Replace them with .

FreeType 1 and GD 1

The PHP team is removing support for both FreeType 1 and GD 1, citing the age and lack of ongoing developments of both libraries as the reason. Newer versions of both of these libraries are available that provide better functionality. For more information about FreeType and GD.

ereg

The ereg extension, which supports Portable Operating System Interface (POSIX) regular expressions, is being removed from core PHP support. If you are using any of the POSIX regex functions, this change will affect you unless you include the ereg functionality. If you’re using POSIX regex today, consider taking the time to update your regex functions to use the Perl-Compatible Regular Expression (PCRE) functions because they give you more features and perform better. Table 1 provides a list of the POSIX regex functions that will not be available after ereg is removed. Their PCRE replacements are also shown.

Table 1. ereg() functions and their PCRE equivalents
ereg() function Similar preg() function
ereg(), eregi() preg_match()
ereg_replace(), ereg_replacei() preg_replace()

PHP V5.3

Some of the features mentioned here have also been ported to PHP V5.3, which is scheduled to be released during the first quarter of 2008. You may want to upgrade to V5.3 and start using these features now, so that when you move to V6 of PHP, it’ll be less of a jump. The following list of features have been back-ported to V5.3:

Namespaces

XMLReader and XMLWriter in core by default

Summary

PHP V6 will offer many improvements and will clean up some of the functionality that has been in older versions of PHP. To take advantage of the new features and cleanup, you can download developer versions of PHP V6 today and start making sure that your applications are unaffected by the changes. You can also take this opportunity to clean up your own scripts, removing any of the deprecated functions mentioned in this article or updating your syntax to make sure that your applications are supported.

Category : Web Support
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