cakephp jquery ajax returns null

Question

am not sure what is happenning here or what i am doing wrong.

my ajax response from cakephp controller returns null when i do console.log() in chrome developer tool. also when i examine the network tab it says no response. here is my code

view.ctp

var formUrl = "<?php echo Router::url(array('controller' => 'ExamsScores','action' => 'ajaxReturn')); ?>";
        //console.log(form);
        //console.log(exam);
        //console.log(formUrl);
        var string = "form="+form + "&exam="+ exam;
        $.ajax({
            type: "POST",
            url: formUrl,
            data: string,
            dataType: "json",
            success: function(response) {
                console.log(response);
            },
            error: function(xhr,status,error) {
                console.log(status);
            }
        });

controller_action

function ajaxReturn(){
    if($this->RequestHandler->isAjax()){
        $this->autoRender = false;
        $form = $this->request->data['form'];
        $exam = $this->request->data['exam'];
        $results = $this->ExamsScore->query("SELECT concat(students.first_name,' ',students.last_name) as NAME,
            exam_type as EXAM,form_name as FORM,sum(score) as TOTAL,avg(score) as MEAN,exams_scores.admission_no from
            students,exams,forms,exams_scores where (exams_scores.admission_no = students.admission_no) and 
            (exams_scores.exam_id = $exam) and (exams.id = $exam) and (students.form_id = $form) and (forms.id = $form)
            group by exams_scores.admission_no order by TOTAL desc 
            ");
    }
    $jsonData = json_encode($results);
    //print_r($jsonData);
    $this->set('response',$jsonData);

here is the catch..

if i comment out the print_r($jsonData) in the controller..the ajax response is null.. if i dont comment it the response comes back as i expect.

what exactly is causing this to happen and why is the response null because i was only using print_r for debugging purposes.

any help ?

Are you planning to create a "How to implement SQL Injections" example website? Because that's what your query looks like. book.cakephp.org/2.0/en/models/… — ndm
– ndm, Commented Mar 1, 2015 at 18:55
And still you managed to create an SQL injection vulnerability. — ndm
– ndm, Commented Mar 1, 2015 at 19:35

nullwriter · Accepted Answer · 2015-03-02 16:07:45Z

1

Ok, several things to note.

Reformat your ajax request as the following:

  var url = window.app.url+"/exams/ajaxReturn"; 

  $.ajax({
        type: "POST",
        url: url,
        data: {form:form,exam:exam},
        dataType: "json",
        success: function(response) {
            console.log(response);
        },
        error: function(xhr,status,error) {
            console.log(status);
        }
    });

Notice how the data field has changed to a different format than yours, this will arrive in the php file as $_POST['form'] and $_POST['exam']

Now, your for your php file:

  function ajaxReturn(){

   $this->request->onlyAllow('ajax');
   $this->autoRender = false;
   $this->layout = 'ajax';

   $form = $this->request->data['form'];
   $exam = $this->request->data['exam'];

   // Other code that was omitted for example purposes

   echo json_encode($results);

}

The first 3 lines ensure that it will only accept ajax requests, and it tells cakephp to not render any .ctp file with the method.

Also, notice how the way I return the json object is with an echo. This is the way to return the json back to the ajax.

answered Mar 2, 2015 at 16:07

nullwriter

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2 Comments

Gordon Over a year ago

thanks Christian.the echo json_encode(); really did what i needed.

nullwriter Over a year ago

@Gordon glad it worked! Would you mind marking it as the answer? Thanks!

Supravat M · Accepted Answer · 2015-03-01 18:20:51Z

0

It says that CakeRequest is now responsible for that. You can find the appropriate paragraph here.

function ajaxReturn(){
    if($this->request->is('ajax')){
        $this->autoRender = false;
        $form = $this->request->data['form'];
        $exam = $this->request->data['exam'];
        $results = $this->ExamsScore->query("SELECT concat(students.first_name,' ',students.last_name) as NAME,
            exam_type as EXAM,form_name as FORM,sum(score) as TOTAL,avg(score) as MEAN,exams_scores.admission_no from
            students,exams,forms,exams_scores where (exams_scores.admission_no = students.admission_no) and 
            (exams_scores.exam_id = $exam) and (exams.id = $exam) and (students.form_id = $form) and (forms.id = $form)
            group by exams_scores.admission_no order by TOTAL desc 
            ");
    }
    $jsonData = json_encode($results);
    //print_r($jsonData);
    $this->set('response',$jsonData);

answered Mar 1, 2015 at 18:20

Supravat M

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1 Comment

Gordon Over a year ago

tried that and no change.just to ask what has the print_r method got to do with the returned data

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