Código PHP:
try{
var radio = document.createElement('<input type="radio" name="radio" />');
}catch(error){
var radio = document.createElement('input');
}
radio.type="radio";
radio.id="box"+fila;
radio.name="radio";
radio.width="22";
radio.height="22";
radio.onclick="return seleccionar(this)";
capa.appendChild(radio);