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PHP object json_encode giving NULL values when echoing?
Class tariff
{

    var $preset_name;
    var $name;
    var $net;
    var $inclusive;
    var $length;
    var $data;


        function __construct()
        {
            $preset_name = "Orange-1gb-ECL";
            $name = array ("1312" => "Orange 1gb Eclipse");
            $net = array ("12312" => "Orange");
            $inclusive = array ("1312" => "1GB");
            $length = array ("12312" => "12 Months");
            $data = array ("12312" => "12p per mb");
        }


}
        $tariff = new tariff();
        $tariff = json_encode($tariff);

    echo $tariff;
    return 0;

$this->preset_name = "Orange-1gb-ECL"; <-- assign to object property

$preset_name = "Orange-1gb-ECL"; <-- assign local variable

$preset_name = "Orange-1gb-ECL";