Some tips.

1. Remove duplicates in array using array_unique

array array_unique ( array $array [, int $sort_flags = SORT_STRING ] )

2. Remove empty elements use array_filter

array array_filter ( array $array [, callable $callback [, int $flag = 0 ]] )

3. value is in the array use in_array

bool in_array ( mixed $needle , array $haystack [, bool $strict = FALSE ] )

4. key exist in array use array_key_exist

bool array_key_exists ( mixed $key , array $array )