How can i check if http is present in img tag

@ade92uk tried a regex-based approach and @cwarn23 / @death_oclock correctly pointed out delimiter problems. Even with fixed delimiters, regex is brittle for HTML. A more robust way is to parse the document with PHP's DOMDocument, loop the <img> elements and test or normalize each src attribute (checks can use stripos for a fast "starts with http" test). This avoids fragile pattern matching and handles malformed tags more gracefully.

libxml_use_internal_errors(true);
$dom = new DOMDocument();
$dom->loadHTML($html);
foreach ($dom->getElementsByTagName('img') as $img) {
    $src = $img->getAttribute('src');
    if (stripos($src, 'http://') === 0 || stripos($src, 'https://') === 0) {
        // already absolute
    } elseif (strpos($src, '//') === 0) {
        $img->setAttribute('src', 'http:' . $src); // or preserve scheme
    } else {
        $img->setAttribute('src', rtrim($base, '/') . '/' . ltrim($src, '/'));
    }
}
echo $dom->saveHTML();

Notes: libxml_use_internal_errors(true) suppresses parse warnings for imperfect HTML. Protocol-relative URLs (starting //) and relative paths require explicit handling when converting to absolute URLs. For strict HTML5 parsing or very broken markup, consider an HTML5 parser or tidy before DOMDocument. Relevant PHP docs: DOMDocument class and libxml_use_internal_errors.