I do not take the javascript form

Well my problem is that I'm on a page called formulario.php and I take the form obviously because it is html but what is javascript does not take it and I would like to know a way to take that code in php and to perform the functions that are there.

CODE:

<form name="formulario1" action="#">
    <select class="seleccion" name="cosa" onchange="cambia()">
        <option value="0">Seleccione
        <option value="1">Juegos
        <option value="2">Hardware
        <option value="3">Software
        <option value="4">Marcas
    </select>

    <select class="seleccion" name="opt">
        <option value="-">-
    </select>

</form>

<script type="text/javascript">
    //1) Definir Las Variables Correspondintes
    var opt_1 = new Array ("-", "Doom", "Forza", "DOTA2", "...");
    var opt_2 = new Array ("-", "Disco Duro", "SSD", "CPU", "...");
    var opt_3 = new Array ("-", "Google Chrome", "Linux", "opera", "...");
    var opt_4 = new Array ("-", "MSI", "ASUS", "GIGABYTE", "...");
    // 2) crear una funcion que permita ejecutar el cambio dinamico

    function cambia(){
        var cosa;
        //Se toma el vamor de la "cosa seleccionada"
        cosa = document.formulario1.cosa[document.formulario1.cosa.selectedIndex].value;
        //se chequea si la "cosa" esta definida
        if(cosa!=0){
            //selecionamos las cosas Correctas
            mis_opts=eval("opt_" + cosa);
            //se calcula el numero de cosas
            num_opts=mis_opts.length;
            //marco el numero de opt en el select
            document.formulario1.opt.length = num_opts;
            //para cada opt del array, la pongo en el select
            for(i=0; i<num_opts; i++){
                document.formulario1.opt.options[i].value=mis_opts[i];
                document.formulario1.opt.options[i].text=mis_opts[i];
            }
            }else{
                //si no habia ninguna opt seleccionada, elimino las cosas del select
                document.formulario1.opt.length = 1;
                //ponemos un guion en la unica opt que he dejado
                document.formulario1.opt.options[0].value="-";
                document.formulario1.opt.options[0].text="-";
            }
            //hacer un reset de las opts
            document.formulario1.opt.options[0].selected = true;

        }



</script>