Under the old Apache Module mode it was possible to manipulate the PHP settings from within a ".htaccess" file placed in the script's top-level directory, this was also recursively applied to all other directories below it.
For example you could turn on the php setting "magic_quotes_gpc" with this line in .htaccess:
php_value magic_quotes_gpc on
Now, when PHP is running as a CGI and phpSuExec protected, manipulating the PHP settings is still possible however you can no longer make use of a ".htaccess" file. Using .htaccess with the required PHP prefix of "php_value" will cause a "500 internal server error" when attempting to access the scripts. This is due to php no longer running as an Apache module, thus Apache is unable to handle those directives any longer.
If your host has, or is, implementing phpSuExec, ALL php values should be removed from your .htaccess files to avoid the 500 internal server error. Instead, you will now be creating and using your own "Local php.ini" file to manipulate the desired php settings.
What is a php.ini file?
The php.ini file is a configuration file that the server looks at to see what PHP options have been made available to the server or what their setting are, if different from the server's default php.ini. While the name may seem advanced to those unfamiliar with it, it is in essence a simple text file with the name php.ini
How to create a php.ini file
To create a php.ini file, just open up a text editor, add in the lines you need and save the file. You can name the file whatever you wish when saving, to ensure the correct FTP transfer mode is used, you might wish to name it "php.ini.txt". Once you have configured all your settings, upload the file to the directory where your script is located and then rename it back to php.ini
For example you can turn on the php setting "magic_quotes_gpc" with this line in php.ini:
magic_quotes_gpc = on
In many cases, you might need to have multiple copies of the same php.ini file in different directories, unlike .htaccess files, php.ini files are not applied recursively to lower directories. If you need the same functionality across all lower directries also, you will then need to copy the php.ini file each directory in turn that will have .php scripts running from within them.