For a complete guide please visit: http://php.net/manual/en/ini.php.
You can find your PHP.INI file in your 'cgi-bin' directory in your hosting account. Below are some of the PHP settings that you can change, including some descriptions on the options that you will see in the file, and what effect changing them might have, or what reasonable limits may be on the ones you may wish to change:
Allow the <? tag. Otherwise, only <?php and <script> tags are recognized.
NOTE: Using short tags should be avoided when developing applications or libraries that are meant for redistribution, or deployment on PHP servers which are not under your control. For portable, redistributable code, be sure not to use short tags.
Allow ASP-style <% %> tags.
Enforce year 2000 compliance (will cause problems with non-compliant browsers). It it recommended to leave this setting on.
If enabled, the request will be allowed to complete even if the user aborts the request. Consider enabling it if executing long request, which may end up being interrupted by the user or a browser timing out.
Maximum execution time of each script, in seconds. The larger the number the more time will be allowed before the script times out.
Maximum amount of time each script may spend parsing request data. If your script has many functions which requires more time to process, consider increasing this number.
Print out errors (as a part of the output). For production web sites, you're strongly encouraged to turn this feature off. Keeping display_errors enabled on a production web site may reveal security information to end users, such as file paths on your Web server, your database schema or other information.
Log errors into a log file, you're strongly advised to use error logging in place of error displaying on production web sites.
Log errors to specified file. This will only work if log_errors = on.
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. If you require register globals, change this setting to on.
Maximum size of POST data that PHP will accept. If you have an upload form and it is timing out, consider increasing this value.
Whether to allow HTTP file uploads. If you do not allow anyone upload files from your website, it is highly recommended to disable this feature for increased security.
Maximum allowed size for uploaded files. If you have an upload form and it is timing out, consider increasing this value.
Defines the default timezone used by the date functions. For a list of valid timezones please review this website:
If your scripts are sending any emails, this is the default path which should not require any changes.