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How can I send JSON data from Javascript in the browser, to a server and have PHP parse it there?
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We can encode and decode JSON objects using PHP programming language. If you use PHP 5.2. 0, then the JSON extension comes bundled and compiled into PHP. JSON is commonly used to read data from a web server and display the data in a web page.
But this fails in the case when we want to receive JSON string as post data. To receive JSON string we can use the “php://input” along with the function file_get_contents() which helps us receive JSON data as a file and read it into a string. Later, we can use the json_decode() function to decode the JSON string.
The php function file_get_contents($url) send a http request to the provided url and returns json data. The function json_decode($json) decodes the provided json string and returns as a PHP object. As simple as that you can parse json response. That was all about getting json from url in php.
I've gotten lots of information here so I wanted to post a solution I discovered.
The problem: Getting JSON data from Javascript on the browser, to the server, and having PHP successfully parse it.
Environment: Javascript in a browser (Firefox) on Windows. LAMP server as remote server: PHP 5.3.2 on Ubuntu.
What works (version 1):
1) JSON is just text. Text in a certain format, but just a text string.
2) In Javascript, var str_json = JSON.stringify(myObject) gives me the JSON string.
3) I use the AJAX XMLHttpRequest object in Javascript to send data to the server:
request= new XMLHttpRequest() request.open("POST", "JSON_Handler.php", true) request.setRequestHeader("Content-type", "application/json") request.send(str_json) [... code to display response ...] 4) On the server, PHP code to read the JSON string:
$str_json = file_get_contents('php://input'); This reads the raw POST data. $str_json now contains the exact JSON string from the browser.
What works (version 2):
1) If I want to use the "application/x-www-form-urlencoded" request header, I need to create a standard POST string of "x=y&a=b[etc]" so that when PHP gets it, it can put it in the $_POST associative array. So, in Javascript in the browser:
var str_json = "json_string=" + (JSON.stringify(myObject)) PHP will now be able to populate the $_POST array when I send str_json via AJAX/XMLHttpRequest as in version 1 above.
Displaying the contents of $_POST['json_string'] will display the JSON string. Using json_decode() on the $_POST array element with the json string will correctly decode that data and put it in an array/object.
The pitfall I ran into:
Initially, I tried to send the JSON string with the header of application/x-www-form-urlencoded and then tried to immediately read it out of the $_POST array in PHP. The $_POST array was always empty. That's because it is expecting data of the form yval=xval&[rinse_and_repeat]. It found no such data, only the JSON string, and it simply threw it away. I examined the request headers, and the POST data was being sent correctly.
Similarly, if I use the application/json header, I again cannot access the sent data via the $_POST array. If you want to use the application/json content-type header, then you must access the raw POST data in PHP, via php://input, not with $_POST.
References:
1) How to access POST data in PHP: How to access POST data in PHP?
2) Details on the application/json type, with some sample objects which can be converted to JSON strings and sent to the server: http://www.ietf.org/rfc/rfc4627.txt
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