500 Internal Server Error with PHP file

Here are some possibilities as to why you are getting 500 errors with php scripts.

When a php script requires write access to a file or directory (like Nucleus does for the 'media'-directory if you want to be able to upload pictures etc), you have to chmod that directory (or file) to 777 (or 666 for files) on most servers. This gives world write access to this folder (file). This is because on most servers apache (and php) runs as user 'nobody'.
Although giving world write access will make it possible to use the script, it also means a security hole, which can be used by hackers and other riff-raff.

To avoid this security hole we run phpsuexec on our servers. Using phpsuexec, php runs under your own username on the server. This removes the necessity to make files and folders world writable. Instead you can just use 755 for folders (the default) and 644 for files (also the default).

Using phpsuexec may have some consequences. Specific statements in your .htaccess file may result in an error 500 (internal server error). So here are two possible problems, and how to solve them:

ForceType

When you are using files with (or without) an extension different then the normal extension for that filetype you can useForceType in your .htaccess file to make it clear to the server how to handle that file (or all the files in the folder) (this works on servers without phpsuexec).
An example: When you have a file called 'item' (like Nucleus uses for FancyURL's) and want it to be parsed by the server as php you use the following code in your .htaccess file:

However, because our servers use phpsuexec this will result in an internal server error. To solve this you can simply useSetHandler instead of ForceType, so your .htaccess-file becomes:

SetHandler application/x-httpd-php

php_value

On a server without phpsuexec it is possible to use the php_value statement in a .htaccess file to change the settings of php (actually overwrite the settings from php.ini). On a sever with phpsuexec this will also result in a server error. To solve this you can use a php.ini file which you put in the same folder as where you would have put your .htaccess file. In that php.ini file you can change all the php values. You only have to put the values you want to modify in that file. By example if you want to set the short_open_tag to Off you would have used short_open_tag? = off in your .htaccess file. Using a php.ini file this results in:

[PHP]

short_open_tag = Off