function html_substr($str, $start, $length = NULL) {
if ($length === 0) return ""; //stop wasting our time ;)
//check if we can simply use the built-in functions
if (strpos($str, '&') === false) { //No entities. Use built-in functions
if ($length === NULL)
return substr($str, $start);
else
return substr($str, $start, $length);
}
// create our array of characters and html entities
$chars = preg_split('/(&[^;\s]+;)|/', $str, -1, PREG_SPLIT_NO_EMPTY | PREG_SPLIT_DELIM_CAPTURE | PREG_SPLIT_OFFSET_CAPTURE);
$html_length = count($chars);
// check if we can predict the return value and save some processing time
if (
($html_length === 0) or
($start >= $html_length) or
(isset($length) and ($length <= -$html_length))
)
return "";
//calculate start position
if ($start >= 0) {
$real_start = $chars[$start][1];
} else { //start'th character from the end of string
$start = max($start,-$html_length);
$real_start = $chars[$html_length+$start][1];
}
if (!isset($length)) // no $length argument passed, return all remaining characters
return substr($str, $real_start);
else if ($length > 0) { // copy $length chars
if ($start+$length >= $html_length) { // return all remaining characters
return substr($str, $real_start);
} else { //return $length characters
return substr($str, $real_start, $chars[max($start,0)+$length][1] - $real_start);
}
} else { //negative $length. Omit $length characters from end
return substr($str, $real_start, $chars[$html_length+$length][1] - $real_start);
}
}
