(PHP 4 >= 4.0.7RC1)get_defined_constants -- Returns an associative array with the names of all the constants and their values.
This function returns the names and values of all the constants currently defined. This includes those created by extensions as well as those created with the define() function.
For example the line below
Array ( [E_ERROR] => 1 [E_WARNING] => 2 [E_PARSE] => 4 [E_NOTICE] => 8 [E_CORE_ERROR] => 16 [E_CORE_WARNING] => 32 [E_COMPILE_ERROR] => 64 [E_COMPILE_WARNING] => 128 [E_USER_ERROR] => 256 [E_USER_WARNING] => 512 [E_USER_NOTICE] => 1024 [E_ALL] => 2047 [TRUE] => 1 )
See also get_loaded_extensions().