Question

Unfortunately I really cannot get my head around regular expressions so my last resort is to ask the help of you fine people.

I have this existing code:

<li id="id-21" class="listClass" data-author="newbie">
    <div class="someDiv">
        <span class="spanClass">Some content</span>
    </div>

    <div class="controls faint">
        <a href="link2">Link 2</a>
        <a href="link3">Link 3</a>
    </div>
</li>

Due to a number of reasons, I have to use preg_replace to inject an additional piece of code:

<a href="link1">Link 1</a>

I think you can guess where that should go, but for the sake of clarity, my desire is for the resulting string to look like:

<li id="id-21" class="listClass" data-author="newbie">
    <div class="someDiv">
        <span class="spanClass">Some content</span>
    </div>

    <div class="controls faint">
        <a href="link1">Link 1</a>
        <a href="link2">Link 2</a>
        <a href="link3">Link 3</a>
    </div>
</li>

Can anyone help me with the appropriate regular expression to achieve this?

Answer 1

try this

$html = '<li id="id-21" class="listClass" data-author="newbie">
    <div class="someDiv">
        <span class="spanClass">Some content</span>
    </div>

    <div class="controls faint">
        <a href="link2">Link 2</a> 
        <a href="link3">Link 3</a>
    </div>
</li>';


$eleName = 'a';
$eleAttr = 'href';
$eleAttrValue = 'link2';
$addBefore = '<a href="link1">Link 1</a>';

$result = regexAddBefore($html, $eleName, $eleAttr, $eleAttrValue, $addBefore);

var_dump($result);

function regexAddBefore($subject, $eleName, $eleAttr, $eleAttrValue, $addBefore){
    $regex = "/(<\s*".$eleName."[^>]*".$eleAttr."\s*=\s*(\"|\')?\s*".$eleAttrValue."\s*(\"|\')?[^>]*>)/s";
    $replace = $addBefore."\r\n$1";

    $subject = preg_replace($regex, $replace, $subject);

    return $subject;
}