function myTruncate($string, $limit, $break=".", $pad="...") {
	// return with no change if string is shorter than $limit
	if(strlen($string) <= $limit)
		return $string; 

	// is $break present between $limit and the end of the string?
	if(false !== ($breakpoint = strpos($string, $break, $limit))) {
		if($breakpoint < strlen($string) - 1) {
			$string = substr($string, 0, $breakpoint) . $pad;
		}
	}
	return $string;
}
/***** Example ****/
$short_string=myTruncate($long_string, 100, ' ');

Truncate text at word break

PHP