PHP Array correct JSON format

Question

I wrote a ajax call which gets an array returned from a .php file (when btn_getAnswers is clicked). Thats working fine so far with integer data (from database). But if I try to return the array filled with three Strings, no response get returned to the ajax call.

Index.html:

<!DOCTYPE html>
<html>
<head>
    <script src="jquery-1.12.3.js"></script> <!-- Import the jquery extension -->
    <script>
        $(document).ready(function(){

            $("#btn_getQuestion").click(function(){
                $.ajax({type :"POST",
                        url: "DBCOMQUESTIONS.php?q=" + $("#input").val(),
                        success: function(result){ //Performs an async AJAX request
                    if(result){
                         $("#output").append(result); //assign the value of the result to the paragraph with the id "output"
                    }
                }});
            }),

            $("#btn_getAnswers").click(function(){
                $.ajax({type :"POST",
                        url: "DBCOMANSWERS.php?q=" + $("#input").val(),
                        dataType:"json",
                        success: function(result){ //Performs an async AJAX request
                    if(result){
                        result.forEach(function(i,v){
                            $("#output").append("<br>" + i);
                        })
                    }
                }});
            });

        });
    </script>
</head>
<body>

<p id="output">This is a paragraph.</p>

<input id="input"/>
<button id="btn_getQuestion">Question</button>
<button id="btn_getAnswers">Answers</button>

</body>
</html>

DBCOMANSWERS.php:

<?php
include("connection.php");  //includes mysqli_connent with database
include("ErrorHandler.php"); //includes error handling function

set_error_handler("ErrorHandler"); //set the new error handler

$q = intval($_GET['q']);
$sql="SELECT * FROM tbl_answers WHERE QID ='".$q."'"; //define sql statement
$query = mysqli_query($con,$sql); // get the data from the db
$result = [];
$i = 0;

while ($row = $query->fetch_array(MYSQLI_NUM)){
    $result[$i] = $row[0];
    $i += 1;
}


mysqli_close($con); // close connection with database
header('Content-Type: application/json');
echo json_encode($result); // return value of $result
?>

If I assign $row[0](or $row[2],$row[3]) to $result[$i] everything works fine. But if I assign $row[1] to $result[$i], the returned "response" is empty, I look it up at "network" of the standard chrome browser development tool.

The only difference between $row[1] and $row[0] and the other columns ([2][3]) is, that the datatype of $row[1] is varchar and the others are int/tinyint.

Obviously the mistake has to be in the last few lines of the .php file. But I don't know what I've done wrong.

For your information: It's about the ajax called which gets triggered when the button with the id "btn_getAnswers" is clicked.

This is the error I am getting from json_encode

Malformed UTF-8 characters, possibly incorrectly encoded

At the end of your PHP script add echo json_last_error_msg(); and see if you're getting a JSON error — Machavity
– Machavity ♦, Commented Apr 8, 2016 at 14:03
@jeroen there is one, as I said the code shown above works absolutely fine when im assigning $row[0],$row[2] or$row[3] to $result. @ Machavity I will give it a try. — flohdieter
– flohdieter, Commented Apr 8, 2016 at 14:06
@Machavity Thank you for this Hint! I've got an error message: "Malformed UTF-8 characters, possibly incorrectly encoded".What does this mean? @ jeroen, the forEach() works. — flohdieter
– flohdieter, Commented Apr 8, 2016 at 14:09
As was hinted at by Machavity, the character in the actual value returned by the database is invalid for json_encode. Use utf8_encode() (on each string) — aaronofleonard
– aaronofleonard, Commented Apr 8, 2016 at 14:10

Machavity · Accepted Answer · 2016-04-08 14:17:20Z

2

So it looks like your database isn't storing UTF-8 characters. As such, you'll need to make sure you convert your characters to UTF-8 before running json_encode

$result = [];

while ($row = $query->fetch_array(MYSQLI_NUM)){
    $result[] = mb_convert_encoding($row[1], 'UTF-8');
}

That should convert your characters to UTF-8. Note that this works with all encodings, while utf8_encode() only works on one

answered Apr 8, 2016 at 14:17

Machavity♦

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Comments

aaronofleonard · Accepted Answer · 2016-04-08 14:17:10Z

1

I'll expand my comment into an actual answer, for anyone in the future to easily be able to see.

$row[1] must contain some characters or data that is/are non-UTF8.

So, use: $result[$i] = utf8_encode($row[0]);

And it will be parseable by json_encode. I've run into this problem many times myself!

answered Apr 8, 2016 at 14:17

aaronofleonard

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