Ajax和jQuery无法将数据正确发送到php

Question

I created a basic form that uses jquery (ajax) to send data to php. PHP should insert a new record based on the data to a mysql database. The reason for this is because I want to make insertions to the database without having to submit the whole form and then use the submit action for something else later. It seems that the jquery works fine since the alert() shows the correct output for the variables, but the PHP does not insert the data and I don't get an error. I can't figure out why this isn't working? I think it is a problem with my $post() because the function underneath does not execute but I can't pinpoint the error. Any help debugging this would be really appreciated. Or if anyone knows another way to get the same functionality that would be great too? Thanks. (The code below works fine now. I figured out it was a type cast error, and I fixed it. Hopefully someone can find this useful!)

<script type="text/javascript">   
    function submitgrade(){
    alert("In it");
    var classID = $("#classSelect").val();
    var student = $("#studentSelect").val();
    var exam = $("#Exam").val();
    var grade = $("#grade").val();
    alert(classID+" - "+student+" - "+exam+" - "+grade);
    $.post('submitgrade.php',{postclassSelect:classID,poststudentSelect:student,postExam:exam,postgrade:grade}, /*1*/
    function(data){
    $("#grade").html("");
    });
    };            
</script>

       <?php       /*submitgrade.php*/


            $con=mysqli_connect("localhost","root","","studentbase");

            // Check connection
            if (mysqli_connect_errno())
            {
                echo "Failed to connect to MySQL: " . mysqli_connect_error();
            }
            $classID = $_POST['postclassSelect'];
            $studentID = $_POST['poststudentSelect'];
            $examID = $_POST['postExam'];
            $grade = $_POST['postgrade'];

            echo $studentID[0]." examID: ". $examID[0];
            $gradequery = "INSERT INTO grade VALUES(".intval($studentID).", '".$classID."', ".intval($examID).", ".intval($grade).");";


            $result = $con->query($gradequery);
            while($row = $result->fetch_assoc())
            {
                echo "<br /><p>Grade of ". $grade." submitted for exam ". $row['exam_id'] ." in ". $row['class_ID'] ."</p>";
            }
        ?>

Answer 1

Have you include this line in your html page ??

<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js">

An example is here again, may help you

<script>
$(document).ready(function(){
 $("input").keyup(function(){
   txt=$("input").val();
   $.post("my_page.asp",{suggest:txt},function(result){
     $("span").html(result);
  });
 });
});

but your code seems correct too buddy !!

Answer 2

I suggest to continue debugging by attaching an error handler to your $.post call, your code could look this:

$.post('submitgrade.php', {postclassSelect:classID,poststudentSelect:student,postExam:exam,postgrade:grade})
.done(function(response) {
    // success
}).fail(function(response) {
    // failure
});

Further more you should check:

• Is the script running on a server? ajax might not work on a file:/// address
• Is the path from javascript location to php file correct?
• what do the browser developer tools say about the request that is initiated?

Answer 3

I fixed it. It was actually just a syntax error in my SQL and a type difference error with one of my database columns. The $grade variable is passed into PHP as a string. Once I wrapped all of my variables in intval() it worked as intended. Stare at the code to long, sometimes you go blind. Haha.

Thank you omnidan for the tip about sanitization. Here is a good guide that I used to apply it to my app:

http://codex.wordpress.org/Validating_Sanitizing_and_Escaping_User_Data