JSON encoded Multidimensional array returns wrong syntax (Unexpected ])

Question

I have an array of arrays in PHP that I need to send to javascript as JSON. The PHP script and AJAX call work, but the returned JSON string is not parse-able JSON; instead of an array of arrays, it just sticks the arrays together with no separators or container.

Example JSON String:

[{"id":"77","options":[],"price":"4.25","title":"Zeppoli's","spec":""}][{"id":"78","options":[],"price":"7.95","title":"Battered Mushrooms","spec":""}]

PHP Snippet that creates above JSON String:

$cartArr = array(); // array of objects to be jsonified
foreach($products as $product){
    unset($newItem);
    $newItem = array(
        "id" => $product['itemID'],
        "options" => $theseOptions,
        "price" => $product['price'],
        "title" => $product['name'],
        "spec" => $product["special"],
        "cartid" => $product['ID']
    );
    array_push($cartArr,$newItem); 
    echo json_encode($cartArr);
}

An attempt to JSON.parse() the string will result in the following error, unless the string is manually corrected.

Uncaught SyntaxError: Unexpected token [

Your JSON is malformed. Each item is an object in its own array, when I believe you only want one array with multiple items. — Brennan
– Brennan, Commented Jun 15, 2016 at 16:36
Put your echo json_encode line outside of the loop. If there are multiple iterations, you end up with invalid JSON from having one after the other. e.g. [][] is invalid JSON. — Jonnix
– Jonnix, Commented Jun 15, 2016 at 16:36

Marc B · Accepted Answer · 2016-06-15 16:40:02Z

2

You're building json in a loop, which means you're outputting MULTIPLE independent json strings, which is illegal syntax. e.g. you're doing

[0,1,2][3,4,5]

which is two separate arrays jammed up against each other. It would have to be more like

[[0,1,2],[3,4,5]]

to be valid JSON. You encode to json LAST, after you've completely build your PHP data structure, not piecemeal in the middle of the construction process.

e.g.

foreach(...) {
   $array[] = more data ...
}
echo json_encode($array);

answered Jun 15, 2016 at 16:40

Marc B

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