echo "<form method='post' action='regprocess.php' id='registerform'>";
echo '<fieldset class="register">';
echo"<h2>Register</h2>";
echo "<ul>";
echo '<li><label for="FirstName">First Name: </label> <input type="text" name="FirstName" id="FirstName"></li>';
echo '<li><label for="LastName">Last Name: </label> <input type="text" name="LastName" id="LastName"></li>';
echo '<li><label for="Email">Email: </label><input type="email" name="Email" id="Email"></li>';
echo '<li><label for="Username">Username: </label><input type="text" name="Username" id="Username"></li>';
echo '<li><input type="button" id="check_username_availability" value="Check Availability"></li>';
echo '<div id="username_availability_result"></div>';
echo '<li><label for="Password">Password: </label><input type="password" name="Password" id="Password"></li>';
echo '<li><input type="submit" value="Register"></li>';
echo "</ul>";
echo "</fieldset>";
echo "</form>";
}
$username = mysql_real_escape_string($_POST['Username']);
//mysql query to select field username if it's equal to the username that we check '
$usernameresult = 'Select Username from User where Username = "'. $username .'"';
$uresult = $conn->query($usernameresult);
//if number of rows fields is bigger them 0 that means it's NOT available '
if($uresult->num_rows==1) {
//and we send 0 to the ajax request
echo 0;
}else{
//else if it's not bigger then 0, then it's available '
//and we send 1 to the ajax request
echo 1;
}
?>
<script src="jquery-1.8.1.min.js" type="text/javascript"></script>
<SCRIPT LANGUAGE="JAVASCRIPT" TYPE="TEXT/JAVASCRIPT">
$(document).ready(function() {
var checking_html = 'Checking...';
//when button is clicked
$('#check_username_availability').click(function(){
//run the character number check
if($('#username').val().length < min_chars){
$('#username_availability_result').html(checking_html);
check_availability();
}
});
});
//function to check username availability
function check_availability(){
//get the username
var username = $('#username').val();
//use ajax to run the check
$.post("check_username.php", { username: username },
function(result){
//if the result is 1
if(result == 1){
//show that the username is available
$('#username_availability_result').html(username + ' is Available');
}else{
//show that the username is NOT available
$('#username_availability_result').html(username + ' is not Available');
}
});
}
</script>
大家好，所以我正在尝试制作一个表单来验证我的数据库中是否有可用的用户名。我以前有点用过 javascript，但我对 Ajax 和 JQuery 做的不多。我在控制台中不断收到这条错误消息，上面写着 ReferenceError: Can't find variable: $ which responds to this line of script $(document).ready(function() {
我不太清楚为什么，我只是想知道是否有人可以给我一些关于如何解决它的见解？谢谢。