limit text length in php and provide 'Read more' link

This is what I use:

// strip tags to avoid breaking any html
$string = strip_tags($string);
if (strlen($string) > 500) {

    // truncate string
    $stringCut = substr($string, 0, 500);
    $endPoint = strrpos($stringCut, ' ');

    //if the string doesn't contain any space then it will cut without word basis.
    $string = $endPoint? substr($stringCut, 0, $endPoint) : substr($stringCut, 0);
    $string .= '... <a href="/this/story">Read More</a>';
}
echo $string;

You can tweak it further but it gets the job done in production.

$num_words = 101;
$words = array();
$words = explode(" ", $original_string, $num_words);
$shown_string = "";

if(count($words) == 101){
   $words[100] = " ... ";
}

$shown_string = implode(" ", $words);