Simple JSON Client with cURL in PHP

JSONClient.php

<?php

class JSONClient {
    private $opt_array = array(
          CURLOPT_RETURNTRANSFER => TRUE,
          CURLOPT_HTTPHEADER => array('Content-type: application/json'));

    private $last_error = NULL;

    public function __construct($opt = array()) {
        if (count($opt) > 0) {
            $opt_array = $opt;
        }
    }

    public function post($url, $content) {
        $handle = curl_init($url);

        curl_setopt_array($handle, $this->opt_array);
        curl_setopt($handle, CURLOPT_POSTFIELDS, json_encode($content));
        $output_json = curl_exec($handle);

        if ($output_json !== FALSE) {
            $this->last_error = NULL;
            return json_decode($output_json, TRUE);
        } else {
            $this->last_error = curl_error($handle);
            return FALSE;
        }
    }

    public function last_error() {
        return $this->last_error;
    }
}