后端error_msg没有发出警报..！

Question

I am using jquery to make a .php file execute but my major problem is when ever a error is thrown from back-end i used a alert to display that error_msg..but ever i submit with a error intentionally...its just moving on to page specified in action...no error alert poped up...plz help me out of this.!!pardon me if am wrong

here gose the DB_Function.php

<?php
class DB_Functions {
    private $db;

    // constructor for database connection
    function __construct() {
        try {
            $hostname = "localhost";
            $dbname = "miisky";
            $dbuser = "root";
            $dbpass = "";
            $this->db = new PDO("mysql:host=$hostname;dbname=$dbname", $dbuser, $dbpass);
        }
        catch(PDOException $e)
        {
            die('Error in database requirments:'    . $e->getMessage());
        }
    }

    /**
      * Storing new user
      * returns user details of user
      */
  public function storeUser($fname, $lname, $email, $password, $mobile) {  
    try {
        $hash = md5($password);
        $sql = "INSERT INTO users(fname, lname, email, password, mobile, created_at) VALUES ('$fname', '$lname', '$email', '$hash', '$mobile', NOW())";
        $dbh = $this->db->prepare($sql);

        if($dbh->execute()){
            // get user details
            $sql = "SELECT * FROM users WHERE email = '$email' LIMIT 1";
            $dbh = $this->db->prepare($sql);
            $result = $dbh->execute();
            $rows = $dbh->fetch();
            $n = count($rows);
            if($n){
                return $rows;
            }
        }
    }
    catch (Exception $e) {
        die('Error accessing database: ' . $e->getMessage());
    }
    return false;
}

/*to check if user is
 already registered*/
  public function isUserExisted($email) {
    try{
        $sql = "SELECT email FROM users WHERE email = '$email' LIMIT 1";
        $dbh = $this->db->prepare($sql);
        $result = $dbh->execute();
        if($dbh->fetch()){
            return true;
        }else{
            return false;
        }
    }catch (Exception $e) {
        die('Error accessing database: ' . $e->getMessage());
    }
}
/*to check if user
exist's by mobile number*/
public function isMobileNumberExisted($mobile){
try{
    $sql = "SELECT mobile FROM users WHERE mobile = '$mobile' LIMIT 1";
    $dbh = $this->db->prepare($sql);
    $result = $dbh->execute();
    if($dbh->fetch()){
    return true;
    }else{
    return false;
    }
}catch(Exception $e){
    die('Error accessing database: ' . $e->getMessage());
}
}
//DB_Functions.php under construction 
//more functions to be added
}
?>

here gose the .php file to be clear on what am doing..!!

<?php
    require_once 'DB_Functions.php';
    $db = new DB_Functions();

    // json response array
    $response = array("error" => false);
    if (!empty($_POST['fname']) && !empty($_POST['lname']) && !empty($_POST['email']) && !empty($_POST['password']) && !empty($_POST['mobile'])){
        // receiving the post params
        $fname = trim($_POST['fname']);
        $lname = trim($_POST['lname']);
        $email = trim($_POST['email']);
        $password = $_POST['password'];
        $mobile = trim($_POST['mobile']);

        // validate your email address
        if(filter_var($email, FILTER_VALIDATE_EMAIL)) {
            //validate your password
            if(strlen($password) > 6){
            //validate your mobile
            if(strlen($mobile) == 12){
            //Check for valid email address
            if ($db->isUserExisted($email)) {
                // user already existed
                $response["error"] = true;
                $response["error_msg"] = "User already existed with " . $email;
                echo json_encode($response);
            } else {
                if($db->isMobileNumberExisted($mobile)) {
                    //user already existed
                    $response["error"] = true;
                    $response["error_msg"] = "user already existed with" . $mobile;
                    echo json_encode($response);
            } else {

                // create a new user
                $user = $db->storeUser($fname, $lname, $email, $password, $mobile);
                if ($user) {
                    // user stored successfully
                    $response["error"] = false;
                    $response["uid"] = $user["id"];
                    $response["user"]["fname"] = $user["fname"];
                    $response["user"]["lname"] = $user["lname"];
                    $response["user"]["email"] = $user["email"];
                    $response["user"]["created_at"] = $user["created_at"];
                    $response["user"]["updated_at"] = $user["updated_at"];
                    echo json_encode($response);
                } else {
                    // user failed to store
                    $response["error"] = true;
                    $response["error_msg"] = "Unknown error occurred in registration!";
                    echo json_encode($response);
                }
            }
         }
        } else {
            $response["error"] = true;
            $response["error_msg"] = "Mobile number is invalid!";
            echo json_encode($response);
        }

        } else {
            //min of 6-charecters
            $response["error"] = true;
            $response["error_msg"] = "password must be of atleast 6-characters!";
            echo json_encode($response);
        }

       } else {
            // invalid email address
            $response["error"] = true;
            $response["error_msg"] = "invalid email address";
            echo json_encode($response);
        }
    } else {
        $response["error"] = true;
        $response["error_msg"] = "Please fill all the required parameters!";
        echo json_encode($response);
    }
?>

and here gose the main file .js

$(document).ready(function(){

    //execute's the function on click
    $("#submit").click(function(e){

        /*jquery to call the url requested 
        and parse the data in json*/
        $.ajax({
            url: "register.php",
            type: "POST",
            data: {
                fname: $("#fname").val(),
                lname: $("#lname").val(),
                email: $("#email").val(),
                password: $("#password").val(),
                mobile: $("#mobile").val()
            },
            dataType: "JSON",
            /*Give out the alert box
            to display the results*/ 
            success: function (json){
                if(json.error){
                    alert(json.error_msg);
                    e.preventDefault();
                }else{
                    alert("Registeration successful!",json.user.email);
                }
            },
            error: function(jqXHR, textStatus, errorThrown){
                alert(errorThrown);
                e.preventDefault();
            }
        });
    });

}); 

and here gose the corresponding .html file

<form method = "POST" name = "register" id = "register" class="m-t" role="form" action="login.html">

                    <div class="form-group">
                        <input type="text" name = "fname" id = "fname" class="form-control" placeholder="First Name" required="">
                    </div>
                    <div class="form-group">
                        <input type="text" name = "lname" id = "lname" class="form-control" placeholder="Last Name" required="">
                    </div>
                    <div class="form-group">
                        <input type="email" name = "email" id = "email" class="form-control" placeholder="Email" required="">
                    </div>
                    <div class="form-group">
                        <input type="password" name = "password" id = "password" class="form-control" placeholder="Password" required="">
                    </div>
                    <div class="form-group">
                        <input type="mobile" name = "mobile" id = "mobile" class="form-control" placeholder="Mobile No" required="">
                    </div>
                    <div  class="form-group" id="recaptcha_widget">
                                                        <div class="required">
                                                          <div class="g-recaptcha" data-sitekey="6Lc4vP4SAAAAABjh8AG"></div>
                                                       <!-- End Thumbnail-->
                                                      </div>
                                                      <?php include("js/captcha.php");?>
                    </div>
                    <div class="form-group">
                            <div cle the terms and policy </label></div>
                    </div>ass="checkbox i-checks"><label> <input type="checkbox"><i></i> Agre
                    <button type="submit" name = "submit" id = "submit" class="btn btn-primary block full-width m-b">Register</button>

                    <p class="text-muted text-center"><small>Already have an account?</small></p>
                    <a class="btn btn-sm btn-white btn-block" href="login.html">Login</a>
                <

/form>

Answer 1

From the comments:

So only after displaying Registeration successful! I want to submit the form and redirect it to login.html

Well the solution is quite simple and involved adding and setting async parameter to false in .ajax(). Setting async to false means that the statement you are calling has to complete before the next statement in your function can be called. If you set async: true then that statement will begin it's execution and the next statement will be called regardless of whether the async statement has completed yet.

Your jQuery should be like this:

$(document).ready(function(){
    //execute's the function on click
    $("#submit").click(function(e){

        /*jquery to call the url requested 
        and parse the data in json*/
        $.ajax({
            url: "register.php",
            type: "POST",
            data: {
                fname: $("#fname").val(),
                lname: $("#lname").val(),
                email: $("#email").val(),
                password: $("#password").val(),
                mobile: $("#mobile").val()
            },
            async: false,
            dataType: "JSON",
            /*Give out the alert box
            to display the results*/ 
            success: function (json){
                if(json.error){
                    alert(json.error_msg);
                    e.preventDefault();
                }else{
                    alert("Registeration successful!",json.user.email);
                    ('#register').submit();
                }
            },
            error: function(jqXHR, textStatus, errorThrown){
                alert(errorThrown);
            }
        });
    });
}); 

So the form will only get submitted if the registration is successful, otherwise not.

Edited:

First of all make sure that <!DOCTYPE html> is there on the top of your page, it stands for html5 and html5 supports required attribute.

Now comes to your front-end validation thing. The HTML5 form validation process is limited to situations where the form is being submitted via a submit button. The Form submission algorithm explicitly says that validation is not performed when the form is submitted via the submit() method. Apparently, the idea is that if you submit a form via JavaScript, you are supposed to do validation.

However, you can request (static) form validation against the constraints defined by HTML5 attributes, using the checkValidity() method.

For the purpose of simplicity I removed your terms and conditions checkbox and Google ReCaptcha. You can incorporate those later in your code.

So here's your HTML code snippet:

<form method = "POST" name = "register" id = "register" class="m-t" role="form" action="login.html">

    <div class="form-group">
        <input type="text" name = "fname" id = "fname" class="form-control" placeholder="First Name" required />
    </div>
    <div class="form-group">
        <input type="text" name = "lname" id = "lname" class="form-control" placeholder="Last Name" required />
    </div>
    <div class="form-group">
        <input type="email" name = "email" id = "email" class="form-control" placeholder="Email" required />
    </div>
    <div class="form-group">
        <input type="password" name = "password" id = "password" class="form-control" placeholder="Password" required />
    </div>
    <div class="form-group">
        <input type="mobile" name = "mobile" id = "mobile" class="form-control" placeholder="Mobile No" required />
    </div>

    <!--Your checkbox goes here-->
    <!--Your Google ReCaptcha-->

    <input type="submit" name = "submit" id = "submit" class="btn btn-primary block full-width m-b" value="Register" />

</form>

<p class="text-muted text-center"><small>Already have an account?</small></p>
<a class="btn btn-sm btn-white btn-block" href="login.html">Login</a>

And your jQuery would be like this:

$(document).ready(function(){

    //execute's the function on click
    $("#submit").click(function(e){

        var status = $('form')[0].checkValidity();
        if(status){
            /*jquery to call the url requested 
            and parse the data in json*/
            $.ajax({
                url: "register.php",
                type: "POST",
                data: {
                    fname: $("#fname").val(),
                    lname: $("#lname").val(),
                    email: $("#email").val(),
                    password: $("#password").val(),
                    mobile: $("#mobile").val()
                },
                async: false,
                dataType: "JSON",
                /*Give out the alert box
                to display the results*/ 
                success: function (json){
                    if(json.error){
                        alert(json.error_msg);
                        e.preventDefault();
                    }else{
                        alert("Registeration successful!",json.user.email);
                        $('#register').submit();
                    }
                },
                error: function(jqXHR, textStatus, errorThrown){
                    alert(errorThrown);
                }
            });
        }

    });

});