Select text following last $ in an expression?

Question

I am using a regular expression to extract the price on the right from the following HTML:

<p class="pricing ats-product-price"><em class="old_price">$99.99</em>$94.99</p>

Using preg match in PHP:

preg_match_all('!<p class="pricing ats-product-price"><em class="old_price">.*?<\/em>(.*?)<\/p>!', $output, $prices);

Except, I noticed that sometimes the HTML doesn't include an old price. So sometimes the HTML looks like this:

<p class="pricing ats-product-price">$129.99</p>

It seems like my goal should be to extract the last price from the expression, or in other words the text that directly follows after the last question mark and before the </p>. This sort of expression is way out of my league though - hoping for some help here. Thanks.

Answer 1

Use a regular expression in combination with a parser:

<?php

$data = <<<DATA
    <p class="pricing ats-product-price">
        <em class="old_price">$99.99</em>
        $94.99
    </p>
    <p class="pricing ats-product-price">$129.99</p>
DATA;

# set up the dom
$dom = new DOMDocument();
$dom->loadHTML($data, LIBXML_HTML_NOIMPLIED | LIBXML_HTML_NODEFDTD);

# set up the xpath
$xpath = new DOMXPath($dom);

$regex = '~\$\d+[\d.]*\b\s*\Z~';
foreach ($xpath->query("//p") as $line) {
    if (preg_match($regex, $line->nodeValue, $match)) {
        echo $match[0] . "\n";
    }
}

This yields

$129.99
$129.99

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The snippet sets up the DOM, queries it for p tags and searches for the last price within.
See a demo for the expression on regex101.com.