使用PHP将大写的H1，H2，...标记转换为大写标题

Question

I would like to turn uppercase h1, h2,... tags into capitalized text with PHP. I'm close, but not there yet. The below snippet does not turn the first character of "LOREM" into uppercase (probably because it tries to uppercase '<'). It would be easy to modify the callback PHP function, but I wish I could do this by only modifying the regex piece:

$var = "
<h1>LOREM IPSUM DOLORES AMET</h1>
THIS IS SOME TEXT
<H2>LOREM IPSUM DOLORES AMET</H2>";

$line = preg_replace_callback(
    '/<h[1-9]>(.*)\>/i',
    function ($matches) {
        return ucfirst(strtolower($matches[0]));
    },
    $var
);

print($line);

Results in:

<h1>lorem ipsum dolores amet</h1>
THIS IS SOME TEXT
<H2>lorem ipsum dolores amet</H2>

Desired output:

<h1>Lorem ipsum dolores amet</h1>
THIS IS SOME TEXT
<H2>Lorem ipsum dolores amet</H2>

Answer 1

Use a DOMDocument

<?php

        $var = "
<h1>LOREM IPSUM DOLORES AMET</h1>
THIS IS SOME TEXT
<H2>LOREM IPSUM DOLORES AMET</H2>";

        $dom = new DOMDocument();
        $dom->loadHTML($var);

        $tags = array("h1", "h2");
        //loop thru all h1 and h2 tags

        foreach ($tags as $tag) {
            //get all elements of the current tag
            $elements = $dom->getElementsByTagName($tag);
            //if we found at least 1 element
            if (!empty($elements)) {
                //loop thru each element of the given tag
                foreach ($elements as $element) {
                    //run ucfirst on the nodevalue
                    //which is equivalent to the "textContent" property of a DOM node
                $element->nodeValue = ucfirst(strtolower($element->nodeValue));
                }
            }
        }

$html = $dom->saveHTML();
//remove extra markup
$html = str_replace("</body></html>","",substr($html,strpos($html,"<h1>"));
echo $html;

<h1>Lorem ipsum dolores amet</h1>
THIS IS SOME TEXT
<h2>Lorem ipsum dolores amet</h2>