Optimize content: first image no lazyload

content.php

<?php

$counter = 0;

$content = preg_replace_callback(
    '/<img([^>]+)>/i',
    function ($matches) use (&$counter) {
        $counter++;
        $imgTag = $matches[0];

        // Remove any existing loading attribute
        $imgTag = preg_replace('/\sloading=["\']?\w+["\']?/i', '', $imgTag);

        if ($counter === 1) {
            // First image: add fetchpriority and no-lazy class
            if (preg_match('/class=["\']([^"\']*)["\']/', $imgTag, $classMatch)) {
                $newClass = trim($classMatch[1] . ' no-lazy');
                $imgTag = preg_replace('/class=["\'][^"\']*["\']/', 'class="' . $newClass . '"', $imgTag);
            } else {
                $imgTag = str_replace('<img', '<img class="no-lazy"', $imgTag);
            }
            $imgTag = str_replace('<img', '<img fetchpriority="high"', $imgTag);

        } else {
            // Subsequent images: lazysizes style
            // Replace src with data-src
            $imgTag = preg_replace('/src=(["\'])(.*?)\1/i', 'data-src=$1$2$1', $imgTag);

            if (preg_match('/class=["\']([^"\']*)["\']/', $imgTag, $classMatch)) {
                $newClass = trim($classMatch[1] . ' lazyload');
                $imgTag = preg_replace('/class=["\'][^"\']*["\']/', 'class="' . $newClass . '"', $imgTag);
            } else {
                $imgTag = str_replace('<img', '<img class="lazyload"', $imgTag);
            }
        }

        return $imgTag;
    },
    $content
);

?>