The natcasesort() function is used to sort an array using a case insensitive "natural array" algorithm. The function implements a sort algorithm but maintains original keys/values.natcasesort() is a case insensitive version of natsort().The natcasesort() function sorts an array by using a "natural order" algorithm. The values keep their original keys.In a natural algorithm, the number 2 is less than the number 10. In computer sorting, 10 is less than 2, because the first number in "10" is less than 2.This function is case-insensitive.This function returns TRUE on success, or FALSE on failure.