Look and say sequence (PHP)

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This is a simple PHP program to generate look-and-say sequences such as the Conway sequence.

function look_and_say($generator, $length) {
  $last_value = "$generator";
  $sequence = array($last_value);
  foreach (range(1, $length) as $i) {
    $next_value = "";
    while ($last_value) {
      preg_match("/$last_value[0]+/", $last_value, $matches);
      $match_len = strlen($matches[0]);
      $next_value .= $match_len . $last_value[0];
      $last_value = substr($last_value, $match_len);
    $last_value = $next_value;
    array_push($sequence, $next_value);
  return $sequence;
$conway = look_and_say(3,10);
foreach ($conway as $x) {
  echo "$x\n";
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