Sending JSON from PHP to JavaScript with AJAX

Question

I am banging my head against the wall here, and I am hoping someone can help me out.

I have an AJAX function which calls a PHP page. That page returns a JSON object, which should then be parsed and displayed to the user. Everything works fine except when the JSON object is returned, trying to parse it gives undefined.

The PHP:

$jsonArray= array(
                'request'  => 'this is the request',
                'response' => 'this is the response'
            );
echo json_encode($jsonArray);

On the Ajax side, I do the following:

var display=xmlHttp.responseText;
alert(display); //gives {"request":"this is the request","response":"This is the response"}
alert(display.request); //gives undefined

Am I missing something obvious? Pasting the same string directly into a JavaScript variable seems to work fine...

don't forget to send the correct headers with your JSON object (text/json). text/html will work because both are text, but it's good practice to send the correct mime type. — zzzzBov
– zzzzBov, Commented Nov 6, 2010 at 3:31
@zzzzBov: No, according to RFC 4627, the correct JSON MIME type is application/json. You can use the PHP code header('Content-type: application/json'); before the echo statement to set this. — PleaseStand
– PleaseStand, Commented Nov 6, 2010 at 6:25
@idealmachine apologies, i didn't look up the correct mime type. My point still stands that text/html will work because both are text. — zzzzBov
– zzzzBov, Commented Nov 6, 2010 at 16:50

Carl Boisvert · Accepted Answer · 2014-04-23 13:14:03Z

2

You will need to parse the json string. JSON.parse should do the tricks. If it's not working, there's probably a problème with the object you encoded.

answered Apr 23, 2014 at 13:14

Carl Boisvert

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GWW · Accepted Answer · 2010-11-06 03:24:09Z

1

You need to parse the JSON data returned from your server. There are many libraries to do this such as:

jQuery,

answered Nov 6, 2010 at 3:24

GWW

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PleaseStand Over a year ago

Documentation for jQuery's $.parseJSON: api.jquery.com/jQuery.parseJSON

ReinaldoNS · Accepted Answer · 2010-11-06 03:27:35Z

1

var myObject = eval('(' + display + ')');

answered Nov 6, 2010 at 3:27

ReinaldoNS

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nonopolarity · Accepted Answer · 2010-11-06 05:54:05Z

0

display is a string. you will need to use

var obj = eval(display)

but eval() is not as safe as using JSON.parse().

edited Nov 6, 2010 at 5:54

answered Nov 6, 2010 at 3:26

nonopolarity

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2 Comments

zzzzBov Over a year ago

Please validate before parsing script from an external source. This is a leading cause in cross-site scripting (XSS).

PleaseStand Over a year ago

The code won't work if an object is returned instead of an array. Parentheses are needed for JavaScript to disambiguate between a) object literal notation, and b) a block of statements.

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