Php, smarty autolink modifier, prevent modifying text with dots into links - php

Question

I'm using smarty for my website and special link modifier that turns into clickable links text from users comments. It works perfect except it is turning such pieces of text as p.s. someword.asag and so on? Is there any way to improve it and prevent such things to happen, keeping it work only on real web links?
function smarty_modifier_autolink($string)
{
$string = preg_replace_callback('#(?:https?://\S+)|(?:www.\S+)|(?:\S+\.\S+)#', function($arr)
{
$email = filter_var($arr[0], FILTER_VALIDATE_EMAIL) === $arr[0] ? true : false;
$origArr0 = $arr[0];
if(strpos($arr[0], 'http://') !== 0 && strpos($arr[0], 'https://') !== 0)
{
$arr[0] = 'http://' . $arr[0];
}
$url = parse_url($arr[0]);
// images
if(isset($url['path'])){
if(preg_match('#\.(png|jpg|gif)$#', $url['path']))
{
return '<img class="img-responsive" src="'. $arr[0] . '" />';
}
}
// youtube
if(in_array($url['host'], array('www.youtube.com', 'youtube.com'))
&& $url['path'] == '/watch'
&& isset($url['query']))
{
parse_str($url['query'], $query);
return sprintf('<div class="embed-responsive embed-responsive-16by9"><iframe class="embed-responsive-item" src="http://www.youtube.com/embed/%s" allowfullscreen></iframe></div>', $query['v']);
}
//links
if($email){
return sprintf('%1$s', $origArr0);
}else{
return sprintf('%2$s', $arr[0], str_replace($url['scheme'].'://', '', $arr[0]));
}
}, $string);
return $string;
}