发布包含http链接的文本字段时，会发生其值错误

I have a form on my web page and on button click i try go post some variables in one of which i hold in its value a http://somelink.com and when the post occurs i get server error, if i take off http:// from the value of the text field everything goes ok.Has anyone any idea what should be this issue? Thank you in

here is part of my form

<form method="post" action="./edit.php" name="one" id="one">
 Name: <input type="text" name="BanName" id="BanName" value=""/><br/>
 Link: <input type="text" name="Link" id="Link" value=""/><br/>
 <input type="button" id="but" name="but" value="Submit"  onClick="document.one.submit();" />
</form>

here is what i get

Forbidden

You don't have permission to access /b/admin/edit.php on this server.

Additionally, a 500 Internal Server Error error was encountered while trying to use an ErrorDocument to handle the request.

PHP Version 5.3.27

After i get the variable with $_POST["Link"] i call this function

 function generateIframeBanner($src){
if(!preg_match('/^http:\/\//',$src)){
    $src='http://'.$src;
}
$html='<iframe src="'.$src.'" frameborder="0" scrolling="no"></iframe>';
return $html;   
   }