How do you pass variables to javascript and back from php?

Question

//Javascript
function updateStudentAttendance(event)
  {
    if ($(this).hasClass('here')) {
  $(this).removeClass('here');
  $(this).addClass('absent');
  var schoolId = $(this).children('p').attr('id');
  var studentId = $(this).attr('id');
  var classId = document.getElementById("classId").value;
  postAttendance(studentId, schoolId, classId, 'Absent');
}

function postAttendance(studentId, schoolId, classId, attendanceEvent)
{
  $.post('post_attendance.php', {
  'studentId': studentId,
  'schoolId': schoolId,
  'event': attendanceEvent,
  'classId': classId
}, function(data) {
 // alert(data);
});
}

//php code looks like this:
<?php
    print sprintf('<div id="%s" class="student span2 well well-small %s">
        <input type="hidden" id="classId" name ="classId" value="%s">'
        , $student->getId(), $class, $classId);
    print '<img src="img/userp.png" style="width: 100%; text-align: center;">';
    print sprintf('<p id="%s" style="text-align: center; font-size: 12px;">%s %s'
        , $_GET['schoolId'], $student->getFirstName, $student->getLastSurname());               
    print '</p>';
    print '</div>';
?>

That's the code I'm using which which pulls the information from the id's and I had to add a hidden element to get the classId. I then post it back after it being modified to update the database with the new information. I feel like this is a terribly odd way to do it and would like to have a better solution for passing these variables.

Please let me know a better way to do this. Thanks!

Cookies or echoed vars or hidden input fields. What you're doing is fine. — Popnoodles
– Popnoodles, Commented Mar 8, 2013 at 16:02
I actually don't really know javascript well, I'm adapting someone elses code. how would you write it to JS? — jakecraige
– jakecraige, Commented Mar 8, 2013 at 16:05

user669677 · Accepted Answer · 2013-03-08 16:05:25Z

2

to PHP

using jquery ajax or using form post

to JS

using hidden input fields with json encoded value (if data stracture is complicated)

answered Mar 8, 2013 at 16:05

user669677

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Comments

Explosion Pills · Accepted Answer · 2013-03-08 16:09:04Z

There are two constructs that I think you can make use of.

One is the HTML5 dataset, which allow you to store custom private data for web applications that is not part of the semantics of the markup. This is more flexible than using id because you can only have one id and it has other purposes. You can have multiple classes, but that too is difficult to use.

The second is the hidden attribute, which declares that an element is not relevant to the page's current state / for use by the user. I sometimes use this attribute to create elements that organize application data that is not relevant to the page markup (I hope this is a correct use, though, but I'm not positive).

soyuka · Accepted Answer · 2013-03-08 16:10:05Z

0

Within your jQuery $.post add some json datatype :

jQuery

 $.post('post_attendance.php', {data:value},
    dataType:"json"
}, function(data) {
   alert(data.error); //will be false
});

Than on your post_attendance.php echo your result with json_encode :

$array = array('response'=>'Some value', error => false);
echo json_encode($array);

answered Mar 8, 2013 at 16:10

soyuka

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Comments

Wesley Schleumer de Góes · Accepted Answer · 2013-03-08 16:23:11Z

You can use an hidden input field and so store a encoded json.

$data = array(
    "key1" => "value1",
    "key2" => "value2"
);
$input = "<input type=\"hidden\" id=\"storage\" value=\"%s\" />";
printf($input, htmlspecialchars(json_encode($data)));

On jQuery

var storage = $.parseJSON($("#storage").val());

Another way is using data attribute, these attributes can be accessed using $("#element").data().

Do some cool changes:

storage["key1"] = "value3";

Back to PHP:

$.post("url.php", storage, function(){
   alert("Alright, bro");
})

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