php将字符串中间部分替换成省略号的功能

/**
 * Reduce a string by the middle, keeps whole words together
 *
 * @param string $string
 * @param int $max (default 50)
 * @param string $replacement (default [...])
 * @return string
 * @author david at ethinkn dot com
 * @author loic at xhtml dot ne
 * @author arne dot hartherz at gmx dot net
 */
function strMiddleReduceWordSensitive($string,$max=50,$rep='[...]'){
  $strlen = strlen($string);
  if ($strlen <= $max)
    return $string;
  $lengthtokeep = $max - strlen($rep);
  $start = 0;
  $end = 0;
  if (($lengthtokeep % 2) == 0) {
    $start = $lengthtokeep / 2;
    $end = $start;
  } else {
    $start = intval($lengthtokeep / 2);
    $end = $start + 1;
  }
  $i = $start;
  $tmp_string = $string;
  while ($i < $strlen) {
    if (isset($tmp_string[$i]) and $tmp_string[$i] == &#39; &#39;) {
      $tmp_string = substr($tmp_string, 0, $i) . $rep;
      $return = $tmp_string;
    }
    $i++;
  }
  $i = $end;
  $tmp_string = strrev ($string);
  while ($i < $strlen) {
    if (isset($tmp_string[$i]) and $tmp_string[$i] == &#39; &#39;) {
      $tmp_string = substr($tmp_string, 0, $i);
      $return .= strrev ($tmp_string);
    }
    $i++;
  }
  return $return;
  return substr($string, 0, $start).$rep.substr($string, - $end);
}

// example:
$text = 'This is a very long test sentence, bla foo bar nothing';
print strMiddleReduceWordSensitive ($text, 30) . "\n";
// Returns: This is a very[...]foo bar nothing (~ 30 chrs)
print strMiddleReduceWordSensitive ($text, 30, '...') . "\n";
// Returns: This is a very...foo bar nothing (~ 30 chrs)