Reading JSON POST using PHP

I looked around a lot before posting this question so my apologies if it is on another post and this is only my second quesiton on here so apologies if I don't format this question correctly.

I have a really simple web service that I have created that needs to take post values and return a JSON encoded array. That all worked fine until I was told I would need to post the form data with a content-type of application/json. Since then I cannot return any values from the web service and it is definitely something to do with how I am filtering their post values.

Basically in my local setup I have created a test page that does the following -

$curl = curl_init();
curl_setopt($curl, CURLOPT_CUSTOMREQUEST, "POST");                                                                     
curl_setopt($curl, CURLOPT_POSTFIELDS, $data);                                                                  
curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);                                                                      
curl_setopt($curl, CURLOPT_HTTPHEADER, array(                                                                          
    'Content-Type: application/json',                                                                                
    'Content-Length: ' . strlen($data))                                                                       
);
curl_setopt($curl, CURLOPT_URL, 'http://webservice.local/');  // Set the url path we want to call
$result = curl_exec($curl);

//see the results
$json=json_decode($result,true);
curl_close($curl);
print_r($json);

On the webservice I have this (I have stripped out some of the functions) -

<?php

header('Content-type: application/json');

/* connect to the db */
$link = mysql_connect('localhost','root','root') or die('Cannot connect to the DB');
mysql_select_db('webservice',$link) or die('Cannot select the DB');

if(isset($_POST['action']) && $_POST['action'] == 'login') {
	$statusCode = array('statusCode'=>1, 'statusDescription'=>'Login Process - Fail');
	$posts[] = array('status'=>$statusCode);
	header('Content-type: application/json');
	echo json_encode($posts);

	/* disconnect from the db */
}
@mysql_close($link);

?>

Basically I know that it is due to the $_POST values not being set but I can't find what I need to put instead of the $_POST. I tried json_decode($_POST), file_get_contents("php://input") and a number of other ways but I was shooting in the dark a bit.

Any help would be greatly appreciated.

Thanks, Steve

Thanks Michael for the help, that was a definite step forward I now have at least got a repsonse when I echo the post....even if it is null

updated CURL -

  $curl = curl_init();
  curl_setopt($curl, CURLOPT_HTTPHEADER, array('Content-Type: application/json')); 
  curl_setopt($ch, CURLOPT_CUSTOMREQUEST, "POST"); 
  curl_setopt($curl, CURLOPT_URL, 'http://webservice.local/');  
  curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
  curl_setopt($curl, CURLOPT_POSTFIELDS, json_encode($data));

updated php on the page that the data is posted to -

$inputJSON = file_get_contents('php://input');
$input= json_decode( $inputJSON, TRUE ); //convert JSON into array

print_r(json_encode($input));

As I say at least I see a response now wheras prior it was returning a blank page

You have empty $_POST. If your web-server wants see data in json-format you need to read the raw input and then parse it with JSON decode.

You need something like that:

$json = file_get_contents('php://input');
$obj = json_decode($json);

Also you have wrong code for testing JSON-communication...

CURLOPT_POSTFIELDS tells curl to encode your parameters as application/x-www-form-urlencoded. You need JSON-string here.

UPDATE

Your php code for test page should be like that:

$data_string = json_encode($data);

$ch = curl_init('http://webservice.local/');
curl_setopt($ch, CURLOPT_CUSTOMREQUEST, "POST");
curl_setopt($ch, CURLOPT_POSTFIELDS, $data_string);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, array(
        'Content-Type: application/json',
        'Content-Length: ' . strlen($data_string))
);

$result = curl_exec($ch);
$result = json_decode($result);
var_dump($result);

Also on your web-service page you should remove one of the lines header('Content-type: application/json');. It must be called only once.

Hello this is a snippet from an old project of mine that uses curl to get ip information from some free ip databases services which reply in json format. I think it might help you.

$ip_srv = array("http://freegeoip.net/json/$this->ip","http://smart-ip.net/geoip-json/$this->ip");

getUserLocation($ip_srv);

Function:

function getUserLocation($services) {
		
		$ctx = stream_context_create(array('http' => array('timeout' => 15))); // 15 seconds timeout

		for ($i = 0; $i < count($services); $i++) {
 
			// Configuring curl options
			$options = array (
				CURLOPT_RETURNTRANSFER => true, // return web page
				//CURLOPT_HEADER => false, // don't return headers
				CURLOPT_HTTPHEADER => array('Content-type: application/json'),
				CURLOPT_FOLLOWLOCATION => true, // follow redirects
				CURLOPT_ENCODING => "", // handle compressed
				CURLOPT_USERAGENT => "test", // who am i
				CURLOPT_AUTOREFERER => true, // set referer on redirect
				CURLOPT_CONNECTTIMEOUT => 5, // timeout on connect
				CURLOPT_TIMEOUT => 5, // timeout on response
				CURLOPT_MAXREDIRS => 10 // stop after 10 redirects
			); 

			// Initializing curl
			$ch = curl_init($services[$i]);
			curl_setopt_array ( $ch, $options );

			$content = curl_exec ( $ch );
			$err = curl_errno ( $ch );
			$errmsg = curl_error ( $ch );
			$header = curl_getinfo ( $ch );
			$httpCode = curl_getinfo ( $ch, CURLINFO_HTTP_CODE );

			curl_close ( $ch );
			
			//echo 'service: ' . $services[$i] . '</br>';
			//echo 'err: '.$err.'</br>';
			//echo 'errmsg: '.$errmsg.'</br>';
			//echo 'httpCode: '.$httpCode.'</br>';
			//print_r($header);
			//print_r(json_decode($content, true));

			if ($err == 0 && $httpCode == 200 && $header['download_content_length'] > 0) {

				return json_decode($content, true);
				
			} 
 
		}
	}

you can put your json in a parameter and send it instead of put only your json in header:

$post_string= 'json_param=' . json_encode($data);

//open connection
$ch = curl_init();

//set the url, number of POST vars, POST data
curl_setopt($ch,CURLOPT_POST, 1);
curl_setopt($ch,CURLOPT_POSTFIELDS, $post_string);
curl_setopt($curl, CURLOPT_URL, 'http://webservice.local/');  // Set the url path we want to call

//execute post
$result = curl_exec($curl);

//see the results
$json=json_decode($result,true);
curl_close($curl);
print_r($json);

on the service side you can get your json string as a parameter:

$json_string = $_POST['json_param'];
$obj = json_decode($json_string);

then you can use your converted data as object.