Delete sections of HTML string using PHP

Question

I have a sting which happens to be HTML, and I wish to delete specific sections of it serverside using PHP (no JavaScript/jQuery solutions please). The string will need to have certain identifiers in it to tag sections which might wish to be removed, and I will also have some variable which indicates which tagged sections should be removed. These indicator tags should not remain in the final modified string.

For instance, consider $html_1 where I included a capture attribute to tag the sections which might be deleted. Or $html_2 where I wrapped [capture] around the tags which might be deleted. Note that these were just two possible ways I thought of tagging the sections, and am okay with any other method which allows the string to be stored in a DB.

For both, I have a <h2> block, <h1> block, and <p> block where capture is used to indicate sections which may or may not be removed. Then given $modify which indicates which sections should or shouldn't be removed, how can I generate the new string which is equal to $html_new? I am thinking maybe a DOMDocument, str_replace, or regex solution might work, but not sure.

<?php

$html_1 = <<<EOT
<div>
    <div>
        <div>
            <h1 capture="a">bla bla bla</h1>
            <p>bla</p>
            <h2 capture="b">bla bla<span>bla</span></h2>
            <h1>bla bla bla bla</h1>
        </div>
    </div>
    <div>
        <p capture="c">bla bla bla</p>
        <h1>bla bla</h1>
    </div>
</div>
EOT;

$html_2 = <<<EOT
<div>
    <div>
        <div>
            [caption id="a"]<h1>bla bla bla</h1>[/caption]
            <p>bla</p>
            [caption id="b"]<h2>bla bla<span>bla</span></h2>[/caption]
            <h1>bla bla bla bla</h1>
        </div>
    </div>
    <div>
        [caption id="c"]<p>bla bla bla</p>[/caption]
        <h1>bla bla</h1>
    </div>
</div>
EOT;

$modify=array('a'=>true,'b'=>false,'c'=>true);

$html_new = <<<EOT
<div>
    <div>
        <div>
            <p>bla</p>
            <h2>bla bla</h2>
            <h1>bla bla bla bla</h1>
        </div>
    </div>
    <div>
        <h1>bla bla</h1>
    </div>
</div>
EOT;
?>

Answer 1

I used $html_2, because I felt it's easier. That should do the trick:

foreach($modify as $letter=>$remove) {
    $pattern = '/\[caption id="' . $letter . '"\](.*)\[\/caption\]/U';
    $replace = ($remove) ? '' : '$1';
    $html_2 = preg_replace($pattern, $replace, $html_2);
}
$html_2 = preg_replace('/^\h*\v+/m', '', $html_2); // Optional: Removing empty lines

In case $remove is false for a certain letter, the matched part of the string get's replaced with the first capture group (which is everything surrounded by the capture tags). If it's true, it get's replaced with an empty string.

Answer 2

You could use preg_replace to replace any line containing capture="a" with a blank line, like this:

$stripped = preg_replace(/^.*(capture="a").*$/, '', $html_1);

If you encased this in a function, you could pass an argument to strip out a, b, or c:

function strip($capture,$block){
    $stripped = preg_replace(/^.*(capture="'.$capture.'").*$/, '', $block);
    return $stripped;
}