find all offsets in a string

utils.offsets.in.func.php

<?php

function offsetsIn(string $haystack, string $needle, $cs=true) : array {
  $offset = false;
  $pos = 0;
  $out = [];
  $func = $cs ? '\strpos' : '\stripos';
  while (strlen($haystack) > 0 && ($pos === 0 || $offset !== false)) {
    if($offset !== false) {
      $out[] = $offset;
    }
    $offset = $func($haystack,$needle,$pos);
    $pos = $offset ? $offset+1 : $pos+1;
  }
  return $out;
}

//
// Tests
//
$testData = [
  offsetsIn("abcdeaaaafghia", 'a'),
  offsetsIn("bcdeaaaafghia", 'a'),
  offsetsIn("bcdefghia", 'a'),
  offsetsIn("abcdeaaaafghi", 'a'),
  offsetsIn("abcdeafghia", 'a'),
  offsetsIn("bcdefghi", 'a'),
];
assert( count( $testData[0] ) === 6);
assert( count( $testData[1] ) === 5);
assert( count( $testData[2] ) === 1);
assert( count( $testData[3] ) === 5);
assert( count( $testData[4] ) === 3);
assert( count( $testData[5] ) === 0);
foreach($testData as $testR) {
  assert( is_array($testR) === true );
}