Question

I’m seeing some peculiar behavior with sending a JSON string back from PHP to Jquery’s $.ajax function.

when I visit my php script from a browser or from calling it via command line with php, it returns completely valid JSON (tested with jsonlint.com). However, when I make an AJAX call from my HTML file I always get NULL back.

Basically from PHP I’m doing this:

// case in a switch that handles command 'getinfo':
$url = "http://someapi.com:1234/api/entity/" . $tagid;
$ch = curl_init( $url );
curl_setopt( $ch, CURLOPT_HEADER, 0 );
curl_setopt( $ch, CURLOPT_USERPWD, "user:pass" );
curl_setopt( $ch, CURLOPT_RETURNTRANSFER, 1 );

$reply = curl_exec( $ch );

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

This spits out this:

[ {
  "class" : "entity",
  "guid" : "IT_EQUIPMENT_abcdef12345677890",
  "retired" : false,
  "deletable" : true,
  "$aAssetTamper" : false
} ]

I’ve tried both with and without RETURNTRANSFER set, and also with and without the header() line. On the HTML side, I am calling with Ajax:

$.ajax({
    url: "gimmedata.php",
    dataType: "json",
    cache: false,
    async: false,
    data: { 'cmd' : 'getinfo', 'tagid' : $('#tag').val },
    success: function( data, textStatus ) {
        // rfcode location
        console.log(data);
    }
});

The status always returns “success”, and the data is always “[]”.

Weird thing is, if I copy the output from the PHP script and then paste it back into the script itself, then echo that string without going through curl, then my AJAX call works fine:

echo '
[ {
  "class" : "entity" 
  "guid" : "IT_EQUIPMENT_abcdef12345677890",
  "retired" : false,
  "deletable" : true,
  "$aAssetTamper" : false
} ]';
return;

$ch = curl_init( $url );
curl_setopt( $ch, CURLOPT_HEADER, 0 );
curl_setopt( $ch, CURLOPT_USERPWD, "user:pass" );
curl_setopt( $ch, CURLOPT_RETURNTRANSFER, 1 );

$reply = curl_exec( $ch );

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

I have no idea what it can be. Any clue? Is curl_exec doing weird things to the text?

Answer 1

Your data passing from JavaScript is wrong:

data: { 'cmd' : 'getinfo', 'tagid' : $('#tag').val },

You should use .val as a function, not as a property:

data: { 'cmd' : 'getinfo', 'tagid' : $('#tag').val() },