php post請求，參數數據格式爲json

function curlPost($url, $post_data, $json){
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 10);
    curl_setopt($ch, CURLOPT_TIMEOUT,        10);
    curl_setopt($ch, CURLOPT_URL, $url);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
    curl_setopt($ch, CURLOPT_POST, 1);
    if ($json) {
        curl_setopt($ch, CURLOPT_HTTPHEADER,array('Content-Type: application/json; charset=utf-8'));
    }
    curl_setopt($ch, CURLOPT_POSTFIELDS, $post_data);
    $output = curl_exec($ch);
    curl_close($ch);
    $output_array = json_decode($output, true);
    return $output_array;
}
$param = '{"id":9,"content":123}';
$result = curlPost("http://localhost",$param,1);
var_dump($result);