how to enumerate items with preg_replace?

Question

I need to add some tags before and after images on document and numerate them at once. HTML Document code is:

....

<img src="http://img.example.com/img/mage1.jpg" alt="sometile"> <br> 
<img src="http://img.example.com/img/image72.jpg" alt="sometile"> <br> 
<img src="http://img.example.com/img/imagstr.jpg" alt="sometile"> <br> 
<img src="http://img.example.com/img/image.jpg" alt="sometile"> <br> 
<img src="http://img.example.com/img/imgger.gif" alt="sometile"> <br> 
<img src="http://img.example.com/img/somepic.png" alt="sometile"> <br> 

I need in result code like this

<div><a name="#pic1"></a><img src="http://img.example.com/img/mage1.jpg" alt="sometile"></div>
<div><a name="#pic2"></a><img src="http://img.example.com/img/image72.jpg" alt="sometile"> </div> 
<div><a name="#pic3"></a><img src="http://img.example.com/img/imagstr.jpg" alt="sometile"> </div> 
<div><a name="#pic4"></a><img src="http://img.example.com/img/image.jpg" alt="sometile"> </div> 
<div><a name="#pic5"></a><img src="http://img.example.com/img/imgger.gif" alt="sometile"> </div> 
<div><a name="#pic6"></a><img src="http://img.example.com/img/somepic.png" alt="sometile"> </div> 

Answer 1

I'm not a fan of regex+HTML, but here goes (I just cooked up a simple regex—you probably already have one):

$s = '<img src="http://img.example.com/img/mage1.jpg" alt="sometile"> <br> 
<img src="http://img.example.com/img/image72.jpg" alt="sometile"> <br> 
<img src="http://img.example.com/img/imagstr.jpg" alt="sometile"> <br> 
<img src="http://img.example.com/img/image.jpg" alt="sometile"> <br> 
<img src="http://img.example.com/img/imgger.gif" alt="sometile"> <br> 
<img src="http://img.example.com/img/somepic.png" alt="sometile"> <br>';

$i = 0;
function wrap($s) {
        global $i;
        $i++;
        return sprintf('<div><a name="pic%d">%s</div>', $i, $s);
}

print preg_replace('#(<img [^>]+?>) <br>#e', "wrap('\\1')", $s);

(Demo)

The important part is the e modifier in the preg_replace(). See "Example #4 Using the 'e' modifier."

---

EDIT
As pointed out in the comments, $i is certainly not the best name for a global variable. If this is going to be used as a simple "one-off" transformation it may be alright. If not, change the name to something that will not conflict. Or put it as a public static in a class.

Also, preg_replace_callback() exists. It's better suited, although I find the passing a function name as a string and evaluating functionName('arg') almost equally ugly :)

Answer 2

As usually, you can also do that with DOM:

$counter = 0;
$doc = new DOMDocument();
$doc->loadHTML($str);
foreach ($doc->getElementsByTagName("img") as $img) {
    $sibling = $img->nextSibling;
    while ($sibling) {
        if ($sibling instanceof DOMElement && $sibling->tagName === 'br') {
            $sibling->parentNode->removeChild($sibling);
        }
        $sibling = $sibling->nextSibling;
    }
    $div = $doc->createElement("div");
    $img->parentNode->replaceChild($div, $img);
    $a = $doc->createElement("a");
    $a->setAttribute("name", "pic" . (++$counter));
    $a->appendChild($img);
    $div->appendChild($a);
}
$str = '';
foreach (simplexml_import_dom($doc->getElementsByTagName("body")->item(0))->children() as $elem) {
    $str .= $elem->asXML();
}

Answer 3

First of all, you are not supposed to use Regexes to deal with HTML.

However, in this case it's easy as you are almost dealing with full lines:

$code = '<img src="http://img.example.com/img/mage1.jpg" alt="sometile"> <br>
<img src="http://img.example.com/img/image72.jpg" alt="sometile"> <br>
<img src="http://img.example.com/img/imagstr.jpg" alt="sometile"> <br>
<img src="http://img.example.com/img/image.jpg" alt="sometile"> <br>
<img src="http://img.example.com/img/imgger.gif" alt="sometile"> <br>
<img src="http://img.example.com/img/somepic.png" alt="sometile"> <br>';

function get_num_row($matches) {
    global $last_num;
    return '<div><a name="pic' . (++$last_num) . '">' . trim($matches[1]) . '</a></div>';
}

$last_num = 0;
$code = preg_replace_callback('/^(.*)<br>$/m', 'get_num_row', $code);
echo $code;

Output:

<div><a name="pic1"><img src="http://img.example.com/img/mage1.jpg" alt="sometile"></a></div>
<div><a name="pic2"><img src="http://img.example.com/img/image72.jpg" alt="sometile"></a></div>
<div><a name="pic3"><img src="http://img.example.com/img/imagstr.jpg" alt="sometile"></a></div>
<div><a name="pic4"><img src="http://img.example.com/img/image.jpg" alt="sometile"></a></div>
<div><a name="pic5"><img src="http://img.example.com/img/imgger.gif" alt="sometile"></a></div>
<div><a name="pic6"><img src="http://img.example.com/img/somepic.png" alt="sometile"></a></div>

Of course you need to set $last_num to 0 if you are going to use the callback again. There's no way to do it without a global or static var. But if you are going to use the callback only once ever you can simply change global $last_num; to static $last_num = 0;. Then it will increment forever with no chance of resetting it - but it won't clutter your global namespace.