PHP unexpected end of input error - php

Question

My PHP code should return a json object of a sql query, but it always throws the error "unexpected end of input". I noticed it doesn't fail if I don't use the variable $row. Here is a snippet of the code:
PHP:
require("pw.php");
class homework {
public $fach;
public $datum;
public $aufgabe;
public function __construct($fach, $datum, $aufgabe) {
$this->fach = $fach;
$this->datum = $datum;
$this->aufgabe = $aufgabe;
}
}
$connection = mysqli_connect($adrs, $usr, $pw, $db);
if(mysqli_connect_errno()) {
die(json_encode(mysqli_connect_error()));
}
if($_POST["feed"] == "hausaufgaben") {
$query = "SELECT fach, datum, aufgabe FROM hausaufgaben WHERE fachgruppe != '";
if($_POST["fremdsprache"] == "latein") {
$query .= "französisch";
}
else {
$query .= "latein";
}
$query .= "' AND fachgruppe != '";
if($_POST["englisch"] == "koch") {
$query .= "schopper";
}
else {
$query .= "koch";
}
$query .= "' AND datum > '" . date("Y-m-d") . "' ORDER BY datum ASC;";
$result = $connection->query($query);
$data = [];
while($row = $result->fetch_row()) {
array_push($data, new homework($row[0], $row[1], $row[2]));
}
echo json_encode($data);
$result->close();
}
$connection->close();
?>
Jquery:
$.ajax({
type: "POST",
url: "php/getFeed.php",
cache: false,
dataType: "json",
data: {feed: "hausaufgaben", fremdsprache: this.fremdsprache, englisch: this.englisch}
})
.done(function(data) {
alert(typeof(data));
document.getElementById("temp").innerHTML = data;
if(typeof(data) != "Object") {
console.log("Error: " + data);
alert("iwas?");
this.hausaufgabenError = true;
this.hausaufgaben = [];
alert(this.hausaufgaben + "\n\n" + this.hausaufgaben.length);
}
else {
this.hausaufgabenError = false;
this.hausaufgaben = data;
}
})
.fail(function(jqXHR, textStatus, error) {
console.log("error: " + error);
alert("iwas?");
this.hausaufgabenError = true;
this.hausaufgaben = [];
alert(this.hausaufgaben + "\n\n" + this.hausaufgaben.length);
});
I hope someone can help me out, because I'm completely stuck :(
Edit: In Mozilla, it thows the error SyntaxError: JSON.parse: unexpected end of data at line 1 column 1 of the JSON data.

Answer 1

In jquery, the command $.parseJSON(''); produces the error you are experiencing. Also, parseJSON will fail similarly if it's given something other than JSON to work with. So my guess is that your php page is either displaying an error, returning no output, or returning JSON mixed with other output.
What to do is either:
fetch the php page in a browser, not via ajax, and look at the output.
or
change the datatype to text for debugging, and use console.log to look at what is actually being sent to your javascript code.