PHP. Can any one help me with preg_match?

I have html code including elements. What I am trying to do is, I need the whole html code of this form element. For example, in the html code below

...
<p>Sample</p>
<img src="..." />
<form method="post" >
    <input type="hidden" value="v1" id="v1" name="task">
    <input type="hidden" value="v2" name="v2">
    ...
</form开发者_JS百科>
<div>...</div>
...

I want to extract these codes:

<form method="post" >
    <input type="hidden" value="v1" id="v1" name="task">
    <input type="hidden" value="v2" name="v2">
    ...
</form>

Since I am not so familiar with preg_match expression, I hardly can figure it out. I googled to understand expressions myself, but only could get small portion of grasp.

Can any one help me, please? Best regards.

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The regular expession to match the form tag may look like this: "(?smi)<form.*?</form>"

EDIT 1: In PHP the function call will look like this: preg_match('/^.*?<form.*?<\/form>.*$/smi', $data)

EDIT 2: This can be tested here: http://www.spaweditor.com/scripts/regex/index.php

But in general case I wouldn't advise as well to use regular expressions for parsing HTML code.

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For something as trivial as matching a form tag in html, just don't use regular expressions or third party xhtml parsers.

Use the the default DOM Parser instead.

It's as simple as :

// Create a new DOM Document to hold our webpage structure 
$xml = new DOMDocument(); 

// Load the html's contents into DOM 
$xml->loadHTML($html); 

$forms = array(); 

//Loop through each <form> tag in the dom and add it to the $forms array 
foreach($xml->getElementsByTagName('form') as $form) { 
    //Get the node's html string
    $forms[] = $form->ownerDocument->saveXML($form); 
}

where $forms is an array of string of every forms.

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Using regular expressions to handle HTML is generally not a good idea. I'd rather suggest to use a HTML parser. I had good results with this library: http://simplehtmldom.sourceforge.net/