Try To Return JSON Data Generated With SQL Statement From PHP Script To JS Webpage But Get Null Instead

I want to return JSON data from a resulted SQL statement in a PHP script upon pressing Submit button, but I receive null instead. I'll be using the returned JSON to filter-show mar

Solution 1:

You can't return the result object of a mysql_query call directly. You first have to parse it with functions like mysql_fetch_array or alike (PHP docu).

...
$result = mysql_query($query);
if ( $result === false ) {
  die("Can\'t do that: " . mysql_error());
}

$retVal = array();
while( $row = mysql_fetch_array( $result ) ) {
  $retVal[] = $row;
}

...
echo json_encode( $retVal );

EDIT

According to the jQuery spec for getJSON (link), the data is sent using GET parameters and not using POST. So you would have to change all the $_POST appearances in your PHP code to either $_GET or $_REQUEST.

Besides this, you should return some error messages if your variables are not set. Right now (according to your code) just an empty document is returned.

Solution 2:

Before the echo you should declare the returned content type:

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

If you want to check for the receival of the data you can use:

$.ajax({
    url: url,
   data: myData,
   success: function(json) {},
   error: function(json) {} // this should allow you to check if data is received (but since the content type is set to text/html and $.getJSON expectr application/json it won't be a success)
});