json - Why null return for PHP array? -

so i've got datafile contain of "events" supposed in json format such: [{"id":"4f946d7a31b27", "title":"floss otter", "start":1333252800, "end":1333339199}]

where more events more json objects [{}, {}, ...]. wrote function try , datafile array of json objects unshift new event onto, , write out datafile, keep getting null return, not array.

if($_server['request_method'] == 'post'){   $title = $_post['title'];   $start = $_post['start'];   $end = $_post['end'];   $event = array(                  'id' => md5($title),                  'title' => $title,                  'start' => $start,                  'end' => $end                  );   $data = get_data();   array_unshift($data, $event);     if ($fp = fopen($data_file, "w")){     fwrite($fp, json_encode($data));     fclose($fp); 

}

}  function get_data() {   $str = "";   if ($fp = fopen($data_file, "r")){     while($line = fgets($fp)) {       $str = $str . $line;     }     $data = json_decode($str, true);     return $data == null ? array() : $data;   } } 

if write out variable $event instead of should array $data, file contains json object should, i'm worried method convert file array incorrect. in advance

try

<?php     function get_data($data_file) {       if (!file_exists($data_file)) {         return array();       }       $str = trim(file_get_contents($data_file));       return 0 < strlen($str) ? json_decode($str, true) : array();     }      if ($_post) {       $title = $_post['title'];       $start = $_post['start'];       $end   = $_post['end'];       $event = array(         'id'    => md5($title),         'title' => $title,         'start' => $start,         'end'   => $end       );        $data_file  = __dir__ . '\file.ext'; // file contains json data       $data_array = get_data($data_file);       array_unshift($data_array, $event);        file_put_contents($data_file, json_encode($data_array));     }