sending data in post method in php with file_get_contents();

<?php

$train_number = $_GET['train_number'];

$postdata = http_build_query(    array(        'train' => $train_number,

        'version' => '2.0'    ));
$opts = array('http' =>    array(        'method'  => 'POST',        'header'  => 'Content-type: application/x-www-form-urlencoded',        'content' => $postdata
    ));
$context  = stream_context_create($opts);
echo file_get_contents('http://etrain.info/ajax.php?q=schedule&v=2.5.2',false, $context);

?>