The filter_list() function returns a list of all supported filters.filter_list — Returns a list of all supported filters
array filter_list ( void )
Returns an array of names of all supported filters, empty array if there are no such filters. Indexes of this array are not filter IDs, they can be obtained with filter_id() from a name instead.
The above example will output something similar to : -
Array ( [0] => int [1] => boolean [2] => float [3] => validate_regexp [4] => validate_url [5] => validate_email [6] => validate_ip [7] => string [8] => stripped [9] => encoded [10] => special_chars [11] => unsafe_raw [12] => email [13] => url [14] => number_int [15] => number_float [16] => magic_quotes [17] => callback )