Untitled

<html>
    <head>
        <title>Buscador</title>
        <meta charset="UTF-8">
        <meta name="viewport" content="width=device-width, initial-scale=1.0">
        <!-- JquerY -->
        <script src="js/jquery-1.11.1.min.js"></script>

    </head>
    <body>
        <input type="hidden" name="elemento_buscar" id="elemento_buscar" value="PR-2014-10-30">
        <?php
            //$variable = document.getElementById("elemento_buscar").value;
           // *** That didnt work ***
           // echo $variable;
           //*** I want to get the input value (value="PR-2014-10-30")
           // into ($variable)
           // to work from here
        ?>
    </body>
</html>