Why is json_encode adding backslashes?

I just came across this issue in some of my scripts too, and it seemed to be happening because I was applying json_encode to an array wrapped inside another array which was also json encoded. It's easy to do if you have multiple foreach loops in a script that creates the data. Always apply json_encode at the end.

Here is what was happening. If you do:

$data[] = json_encode(['test' => 'one', 'test' => '2']);
$data[] = json_encode(['test' => 'two', 'test' => 'four']);
echo json_encode($data);

The result is:

["{\"test\":\"2\"}","{\"test\":\"four\"}"]

So, what you actually need to do is:

$data[] = ['test' => 'one', 'test' => '2'];
$data[] = ['test' => 'two', 'test' => 'four'];
echo json_encode($data);

And this will return

[{"test":"2"},{"test":"four"}]

Just use the "JSON_UNESCAPED_SLASHES" Option (added after version 5.4).

json_encode($array,JSON_UNESCAPED_SLASHES);