<script>
    function showUser(str) {
        if (str == "") {
            document.getElementById("txtHint").innerHTML = "";
            return;
        } else {
            if (window.XMLHttpRequest) {
                // code for IE7+, Firefox, Chrome, Opera, Safari
                xmlhttp = new XMLHttpRequest();
            } else {
                // code for IE6, IE5
                xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
            }
            xmlhttp.onreadystatechange = function() {
                if (this.readyState == 4 && this.status == 200) {
                    var myObj = JSON.parse(this.responseText);
                    var horas = document.getElementsByClassName("hora");
                    var i, x, bandeira = 0;
                    for (x in myObj) {
                        for (i = 0; i < horas.length; i++) {
                            if (horas[i].value == myObj[x]) {

                                horas[i].disabled = true;
                                bandeira++;
                                break;
                            } else {
                                horas[i].disabled = false;
                            }
                        }
                    }

                    //alert(this.responseText);
                }
            };
            xmlhttp.open("GET", "verificar_marcacao.php?q=" + str, true);
            xmlhttp.send();
        }
    }

</script>