Question

Test input : dog, dog, cat, cow, dog, horse, cat, dog

valid output : dog, cat, cow, horse

Probably insignificant details : this is for an email function Im writing, where a list of parts are associated with an email address, and I want to ‘lump’ all the parts that go to the same address together. Using php. I think solving the test case would solve my problem.

Answer 1

$string = implode(', ', array_unique(array_filter(array_map('trim', explode(',', $string))))));

From inner to outer

• Split at ,
• remove any leading and trailing whitespace
• if needed remove any empty string
• return only unique string
• implode with , again