PHP - ONKEY ME VA a otra pagina distinta

<script>

function onKeyDownHandler(event) {

    var codigo = event.which || event.keyCode;

    console.log("Presionada: " + codigo);

    if(codigo === 13){

      UUGIG=document.getElementsByName("A")[0].value;

        window.location.href='b.php?

    }

}

</script>

<span style="  padding: 10px;

color: black;

font-family: arial, helvetica;

font-size: 120%;

font-weight: bold;

left:40%;

top:50%;

position:absolute;

">

   <div style=" color: blue; font-family: arial,helvetica; font-size: 120%; font-weight: bold;">

pizza<br><br>  <i style="align-items:center;color:#403A3A;;"class="fa fa-qrcode fa-lg fa-fw"></i>  <input onkeydown="onKeyDownHandler(event)" type="text" id="a" name="a"><br><br>