preg_match all paragraphs in a string

Question

The following string contains multiple

tags. I want to match the contents of each of the

with a pattern, and if it matches, I want

Answer 1

Use a combination of SimpleXML, XPath and regular expressions (regex on text(), etc. are only supported as of XPath 2.0).
The steps:

1. Load the DOM first
2. Get all p tags via an xpath query
3. If the text / node value matches your regex, apply a css class

This is the actual code:

para 1
نص عربي أو فارسي
para3
";
$xml = simplexml_load_string($html);

# query the dom for all p tags
$ptags = $xml->xpath("//p");

# your regex
$regex = '~[\x{0590}-\x{05ff}\x{0600}-\x{06ff}]~u';

# alternatively:
# $regex = '~\p{Arabic}~u';

# loop over the tags, if the regex matches, add another attribute
foreach ($ptags as &$p) {
    if (preg_match($regex, (string) $p))
        $p->addAttribute('class', 'some cool css class');
}

# just to be sure the tags have been altered
echo $xml->asXML();

?>

See a demo on ideone.com. The code has the advantage that you only analyze the content of the p tag, not the DOM structure in general.