POST, AJAX, and PHP : JSON submission

Question

Ok, so here is my JS/jQuery code, my rate.php file simply has a print_r($_POST) in it. The problem is, the $_POST is accepting rated as the string "Array", rather than the actual array as I have defined it. How do I correct this code so PHP will recognize the JSON input as a proper array, rather than a string?

var rated = {"key" : key , "value" : value};

$.ajax({
  type: "POST",
  url: $(location).attr('protocol') + "//" + $(location).attr('hostname') + "/ajax/rate.php",
  data: {
    "rated" : rated
  },
  success: function(data) {
    alert(data);
  }
});

This is the output message I'm getting:

Array ( [rated] => Array )
Fatal error: Only variables can be passed by reference in .../ajax/rate.php on line X

EDIT: There are actually more variables that rated, but none of them are arrays (thus there isn't an issue with them), so I cut them out of the code above for brevity sake.

gdub · Accepted Answer · 2011-10-23 22:58:34Z

When passing JSON data to your php script through ajax I would recommend string encoding the JSON data and then parsing it on the server side.

var rated = {"key" : key , "value" : value};
var rated_encoded = JSON.stringify(rated);

$.ajax({
  type: "POST",
  url: $(location).attr('protocol') + "//" + $(location).attr('hostname') +     "/ajax/rate.php",
  data: {
    "rated" : rated_encoded
  },
  success: function(data) {
    alert(data);
  }
});

Then you should be able to access the POST variable in your PHP script using $_POST as with any other scalar value. Once you have the JSON string 'rating_encoded' on the server-side, parse it to an associative array using PHP's json_decode().

if(isset($_POST["rated"])){
    $rated_json = $_POST["rated"];
    $JSONArray  = json_decode($rated_json, true); //returns null if not decoded
    //Values can now be accessed like standard PHP array
    if($JSONArray !== null){ 
        $key = $JSONArray["key"];
        $value = $JSONArray["value"];
    }
}

I've found that this method is very effective for transferring javascript object data to the server and vice versa (using PHP's json_encode() to translate PHP arrays into valid javascript objects)

Ilia G · Accepted Answer · 2011-10-23 05:30:23Z

0

It is a proper array, just not what you expect it to be. What you likely want can be achieved by simply passing rated to the data parameter as is. I.e.

var rated = {"key" : key , "value" : value};

$.ajax({
  type: "POST",
  url: $(location).attr('protocol') + "//" + $(location).attr('hostname') + "/ajax/rate.php",
  data: rated,
  success: function(data) {
    alert(data);
  }
});

answered Oct 23, 2011 at 5:30

Ilia G

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2 Comments

Matt Over a year ago

There are actually more variables that rated, but none of them are arrays (thus there isn't an issue with them), so I cut them out of the code above for brevity sake.

Ilia G Over a year ago

@Matt, then what is the request data are you expecting? Because right not you are passing parameter rated with value {"key" : key, "value" : value} and HTTP doesn't support parameter nesting.

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