Add the ability to disable the PHP Code execution feature by using a new 'post_snippets_php_execution_enabled ' filter

To disable the "PHP Code" execution feature, add the following code your theme's functions.php file:

add_filter('post_snippets_php_execution_enabled', '__return_false');

As per this suggestion: http://wordpress.org/support/topic/disabling-php-code-functionality
Merge pull request #1 from OM4/develop

Add the ability to disable the PHP Code execution feature