Question

I have an array, such as this example:

Array
(
    [0] => cinema
    [1] => school
    [2] => college
    [3] => social
    [4] => cinema
    [5] => School
    [6] => COllEGE
    [7] => Ccccccc
)

I want only whole words that start from ‘C’ or ‘S’ only one time,
repetition character in word is allowed irrespective of whether they are upper or lower case

Example output:

cinema
college
ccccccc

Answer 1

Use array_filter with a simple filter (regex or $val[0] == "c" for instance) and array_unique

Here is an example (not tested) :

$data = array(...data...);

function check_value($val) {
  return preg_match('/^c/i', $val);
}

$output = array_unique(array_filter($data, 'check_value'));