Why does `json_encode` add backslashes and how can I prevent it?

Json_encode Adds Backslashes: Unveiling the Mystery

In the realm of JavaScript, json_encode has long been a trusted ally for encoding data into JSON format. However, some developers have encountered an unexpected phenomenon where json_encode introduces backslashes into the output.

The Uploading Conundrum

One such instance occurs when using json_encode to return JSON data after a file upload. Consider the following code:

print_r($result); // Associative array

$encoded_result = json_encode($result); // Valid JSON

echo $encoded_result;

The Unexplained Backslashes

To the surprise of the developer, the resulting JSON includes unwanted backslashes:

{"logo_url":"http:\/\/mysite.com\/uploads\/gallery\/7f\/3b\/f65ab8165d_logo.jpeg","img_id":"54","feedback":{"message":"File uploaded","success":true}}

Pinpointing the Culprit

Initial investigations revealed that the backslashes were being added somewhere between json_encode and the browser's parsing of the JSON data.

alert(data.toSource()); // Result: invalid JSON with added "status:200"

The Hidden Variable

Closer examination uncovered an unexpected culprit: the Plupload bind event.

uploader.bind('FileUploaded', function(up, file, data) {
  alert(data.toSource());
  $('#' + file.id + " b").html("100%");
});

Plupload, a popular file upload library, appeared to be manipulating the returned data, adding the "status:200" property and encoding the slashes.

The Solution: Escaping the Slashes

To thwart the unwanted backslashes, the code was modified to include the "JSON_UNESCAPED_SLASHES" option in the json_encode function call:

$encoded_result = json_encode($result, JSON_UNESCAPED_SLASHES);

This option effectively disables the escaping of forward slashes, resulting in the desired JSON output:

{"logo_url":"http://mysite.com/uploads/gallery/7f/3b/f65ab8165d_logo.jpeg","img_id":"54","feedback":{"message":"File uploaded","success":true}}

Unveiling the Truth

In conclusion, the addition of backslashes in json_encode output was attributed to the unintended manipulation of data by the Plupload bind event. By incorporating the "JSON_UNESCAPED_SLASHES" option, developers can prevent this unwanted escape character from interfering with their JSON data.

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