There were some new php.ini directives introduced in PHP 5. Here is a list of them:
mail.force_extra_parameters - Force the addition of the specified parameters to be passed as extra parameters to the sendmail binary. These parameters will always replace the value of the 5th parameter to mail(), even in safe mode
register_long_arrays - allow/disallow PHP to register the deprecated long $HTTP_*_VARS
session.hash_function - select a hash function (MD5 or SHA-1)
session.hash_bits_per_character - define how many bits are stored in each character when converting the binary hash data to something readable (from 4 to 6)
zend.ze1_compatibility_mode - Enable compatibility mode with Zend Engine 1 (PHP 4)