Question

I have the following array:

Array
(
    [0] => BCD
    [1] => ACE
    [2] => AHP
    [3] => BGH
    [4] => ART
    [5] => COT
    [6] => ARG
    [7] => BGT
)

I need to match all elements whose first letter is in the following array:

Array
(
    [0] => B
    [1] => A
)

to get:

Array
(
    [0] => ACE
    [1] => AHP
    [2] => BGH
    [3] => ART
    [4] => ARG
    [5] => BGT
)

Short of looping through the whole array, how do I do this in PHP? Is there a built-in PHP array function for this or a combination of so? The order does not matter for both keys and values of the resulting array. Thanks much.

Answer 1

You can use array_filter for these operations:

$array = array('CBD', 'NHN', 'NHP', 'WHC', 'NND', 'CQN', 'WST', 'WVT');

$whitelist = array('W', 'N');

$filtered = array_filter($array, function($val) use ($whitelist) {
  // check if first letter is in the whitelist array
  if (in_array($val{0}, $whitelist)) {
    return $val;
  }
  return false;
});

Output:

Array
(
    [1] => NHN
    [2] => NHP
    [3] => WHC
    [4] => NND
    [6] => WST
    [7] => WVT
)