How can I count the amount of lines of an HTML code with PHP?

Question

I have some HTML generated by a WYSIWYG-editor (WordPress).
I'd like to show a preview of this HTML, by only showing up to 3 lines of text (in HTML format).

Example HTML: (always formated with new lines)

<p>Hello, this is some generated HTML.</p>
<ol>
    <li>Some list item<li>
    <li>Some list item</li>
    <li>Some list item</li>
</ol>

I'd like to preview a maximum of 4 lines of text in this formated HTML.

Example preview to display: (numbers represent line numbers, not actual output).

1. Hello, this is some generated HTML.
3. Some list item
4. Some list item

Would this be possible with Regex, or is there any other method that I could use?
I know this would be possible with JavaScript in a 'hacky' way, as questioned and answered on this post .
But I'd like to do this purely on the server-side (with PHP), possibly with SimpleXML?

Answer 1

It's really easy with XPath:

$string = '<p>Hello, this is some generated HTML.</p>
    <ol>
        <li>Some list item</li>
        <li>Some list item</li>
        <li>Some list item</li>
    </ol>';

// Convert to SimpleXML object
// A root element is required so we can just blindly add this
// or else SimpleXMLElement will complain
$xml = new SimpleXMLElement('<root>'.$string.'</root>');

// Get all the text() nodes
// I believe there is a way to select non-empty nodes here but we'll leave that logic for PHP
$result = $xml->xpath('//text()');

// Loop the nodes and display 4 non-empty text nodes
$i = 0;
foreach( $result as $key => $node )
{
    if(trim($node) !== '')
    {
        echo ++$i.'. '.htmlentities(trim($node)).'<br />'.PHP_EOL;
        if($i === 4)
        {
            break;
        }
    }
}

Output:

1. Hello, this is some generated HTML.<br />
2. Some list item<br />
3. Some list item<br />
4. Some list item<br />

Answer 2

I have personally coded the following function, which isn't perfect, but works fine for me.

function returnHtmlLines($html, $amountOfLines = 4) {
    $lines_arr = array_values(array_filter(preg_split('/\n|\r/', $html)));

    $linesToReturn = array_slice($lines_arr, 0, $amountOfLines);

    return preg_replace('/\s{2,}/m', '', implode('', $linesToReturn));
}

Which returns the following HTML when using echo :

<p>Hello, this is some generated HTML.</p><ol><li>Some list item<li><li>Some list item</li>

Or formatted:

<p>Hello, this is some generated HTML.</p>
<ol>
    <li>Some list item<li>
    <li>Some list item</li>

Browsers will automatically close the <ol> tag, so it works fine for my needs.

Here is a Sandbox example