recursive string scanner

scan_until.php

<?php

function scan_until($subject, $search, $position = 0, $match_position = 0, $buffer = '') {
  $char = substr($subject, $position, 1); // take of a character
  $position += 1; // increment our subject position

  if ($position == strlen($subject)) { // are we at the end and haven't found shit?
    return $subject;
  }

  if ($char == substr($search, $match_position, 1)) { // have we matched anything?
    $match_position += 1; // we got a match, quick increment!
  } else {
    $match_position = 0; // no match this run, so reset the position, it's all or nothing!
  }

  if ($match_position > 0 && strlen($search) == $match_position) { // is the match completed?
    return substr($buffer, 0, -strlen($search)+1); // return the buffer, but take the search off the end
  }

  return scan_until($subject, $search, $position, $match_position, $buffer . $char); // keep looking recursively
}

echo "'" . scan_until('I like to eat lollies.', 'lollies') . "'\n"; // => 'I like to eat '
echo "'" . scan_until('I like to eat lollies.', 'poop') . "'\n";    // => 'I like to eat lollies.'
echo "'" . scan_until('I like to eat lollies.', 'too') . "'\n";     // => 'I like to eat lollies.'