How would I be able to populate all empty href attributes using php based on a condition?

Question

I'm trying to replace all empty href attributes in my php file based on a condition. I've tried using str_repalce() but that doesn't seem to work.

I don't want to use DOMDocument as I think it wouldn't be necessary because what I'm trying to do's look for all href attributes in my php file, which are currently empty, and replacing them with a link.

I've seen this question asked before but it didn't seem to work for me.

Side note: I currently have an <img> inside all of my <a href="">s (<a href=""><img/></a>). I only want to populate the empty href attributes.

How can I achieve this?

$getQueryParam = $_GET['type'];

switch ($getQueryParam) {
    case 'blue':
        preg_replace('/^<a href="#(.*?)"[^>]+>(.*?)<\/a>/', '', 'mylink.com');
        break;
}

score 0 · Answer 1 · answered Feb 11 '21 at 21:27

First, obligatory "do not parse HTML with RegEx" followed by "if you control the HTML it might be safe".

You're definition of "empty" is a little vague. Your sample is using literally empty but the RegEx you are showing has a # in it. Regardless, I came up with two ways.

I personally don't like preg_replace too much unless I'm using it to remove something, but that's just me, and it isn't wrong to use. This first example just looks for an opening <a tag, followed by non-greedy match for non-closing tag >, followed by an href=", a hash or space, a closing " and anything else until >. This can very easily break, for instance if you have spaces around the href = or if you use different quotes, but that's a bridge to cross later possibly.

$testData = [
    '<a href=""><img/></a>',
    '<a href="#"><img/></a>',
    '<a class="button" href="#" rel="nofollow"><img/></a>',
    '<a href=""><img/></a>',
];

foreach ($testData as $test) {
    echo preg_replace('/(<a[^>]*?href=")(?:#|\s+)?("[^>]*>)/', '$1https://example.com$2', $test), PHP_EOL;
}

The second version uses DOMDocument which I know you said you didn't want to use, but honestly it allows you to reason about things such better, to the point that I don't think it needs any more comment.

$testData = [
    '<a href=""><img/></a>',
    '<a href="#"><img/></a>',
    '<a class="button" href="#" rel="nofollow"><img/></a>',
    '<a href=""><img/></a>',
];

foreach ($testData as $test) {
    $d = new DOMDocument();
    $d->loadHTML($test, LIBXML_HTML_NOIMPLIED | LIBXML_HTML_NODEFDTD);
    foreach ($d->getElementsByTagName('a') as $tag) {
        if (in_array(trim($tag->getAttribute('href')), ['#', ''], true)) {
            $tag->setAttribute('href', 'https://example.com');
        }
    }
    echo $d->saveHTML(), PHP_EOL;
}

I will note, the DOMDocument might change your HTML just slightly, however for most people these days, HTML vs XHTML doesn't really matter much anymore.

How would I be able to populate all empty href attributes using php based on a condition?

1 Answers1