Add class to Regex result in preg_replace

Question

I would like to add the class with regex and preg_replace

echo preg_replace("/<li\>\s*<p\>[a-z]\)\s/", "/<li class=\"inciso\"\>\s*<p\>[a-z]\)\s/", $documento);

This is the model of the lines of my document:

<li>
  <p>a) longo texto</p>
</li>

Answer 1

It seems to me that you didn’t understand the function preg_replace, because you passed a regular expression as the second parameter, when you should use the text that should replace what was found.

In addition you are escaping (with backslash) the characters > which has no special function in regular expression.

To make your code work you must use a subpater (group delimited with parentheses) and references ($n where n is a number):

preg_replace('/<li>(\s*<p>[a-z]\)\s)/', '<li class="inciso">$1', $documento);

The explanation of this regular expression can be found in that reply

Answer 2

Use Regex with HTML it’s not a good idea.

Instead you can use the DOM:

<?php

$dom = new DomDocument;
$dom->loadHTML("<li><p>a) longo texto</p></li>");

$lis = $dom->getElementsByTagName('li');

foreach ($lis as $li) {

    $li->setAttribute('class', 'inciso');

}