Cut off a piece of a string based on character indices and counts. Follows the same behavior as PHP's own substr() function.

Note that for cutting off a string at a known character/substring location, the usage of PHP's normal strpos/substr is safe and much faster.

File

drupal-6.x/includes/unicode.inc, line 475

Code

function drupal_substr($text, $start, $length = NULL) {
  global $multibyte;
  if ($multibyte == UNICODE_MULTIBYTE) {
    return $length === NULL ? mb_substr($text, $start) : mb_substr($text, $start, $length);
  }
  else {
    $strlen = strlen($text);
    // Find the starting byte offset
    $bytes = 0;
    if ($start > 0) {
      // Count all the continuation bytes from the start until we have found
      // $start characters
      $bytes = -1;
      $chars = -1;
      while ($bytes < $strlen && $chars < $start) {
        $bytes++;
        $c = ord($text[$bytes]);
        if ($c < 0x80 || $c >= 0xC0) {
          $chars++;
        }
      }
    }
    else if ($start < 0) {
      // Count all the continuation bytes from the end until we have found
      // abs($start) characters
      $start = abs($start);
      $bytes = $strlen;
      $chars = 0;
      while ($bytes > 0 && $chars < $start) {
        $bytes--;
        $c = ord($text[$bytes]);
        if ($c < 0x80 || $c >= 0xC0) {
          $chars++;
        }
      }
    }
    $istart = $bytes;

    // Find the ending byte offset
    if ($length === NULL) {
      $bytes = $strlen - 1;
    }
    else if ($length > 0) {
      // Count all the continuation bytes from the starting index until we have
      // found $length + 1 characters. Then backtrack one byte.
      $bytes = $istart;
      $chars = 0;
      while ($bytes < $strlen && $chars < $length) {
        $bytes++;
        $c = ord($text[$bytes]);
        if ($c < 0x80 || $c >= 0xC0) {
          $chars++;
        }
      }
      $bytes--;
    }
    else if ($length < 0) {
      // Count all the continuation bytes from the end until we have found
      // abs($length) characters
      $length = abs($length);
      $bytes = $strlen - 1;
      $chars = 0;
      while ($bytes >= 0 && $chars < $length) {
        $c = ord($text[$bytes]);
        if ($c < 0x80 || $c >= 0xC0) {
          $chars++;
        }
        $bytes--;
      }
    }
    $iend = $bytes;

    return substr($text, $istart, max(0, $iend - $istart + 1));
  }
}