Php: get response from a posted form on an external service - php

Question

This would seem an easy task, but I can't get it to work.
I need to access some data publicly provided by the Bank of Mexico. The data is available through a form you can find at the link: http://www.banxico.org.mx/SieInternet/consultarDirectorioInternetAction.do?accion=consultarCuadro&idCuadro=CP5&locale=es
You can see an example of the data I need by clicking on the button "html" on the top left section. Once that table is opened I know how to fetch the data I need and work with them. However, I'd like to have this as an automated task so that the script can check regularly when new data is available.
So, I am trying to use file_get_contents() along with stream_context_create() to post the parameters I need and open the result page, so I can work with it.
I tried a few different ways (first I was using http_post_fields() ), but nothing seems to work.
Right now my code is this:
<?php
$url = 'http://www.banxico.org.mx/SieInternet/consultarDirectorioInternetAction.do?accion=consultarSeries';
$data = array(
'anoFinal' => 2015,
'anoInicial' => 2015,
'formatoHTML.x' => 15,
'formatoHTML.y' => 7,
'formatoHorizontal' => false,
'idCuadro' => 'CP5',
'locale' => 'es',
'sector' => 8,
'series' => 'SP1',
'tipoInformacion' => '',
'version' => 2
);
$postdata = http_build_query($data);
$opts = array('http' =>
array(
'method' => 'POST',
'header' => 'Content-type: application/x-www-form-urlencoded',
'content' => $postdata
)
);
$context = stream_context_create($opts);
$result = file_get_contents($url, false, $context);
//returns bool(false)
?>
What am I missing? I noticed that the page does in fact return nothing if wrong parameters are sent (as you can see by opening simply http://www.banxico.org.mx/SieInternet/consultarDirectorioInternetAction.do?accion=consultarSeries without any post data: nothing is returned), thus I'm not sure whether the post is successful but nothing is returned because some parameters are wrong, or if the code is wrong.
The posted data should be fine, as I copied them directly from a successfull query I made manually.
What am I missing?

Answer 1

It turns out cURL is a better way to do this, thanks to CBroe for the advice.
Here is the fixed code I am using, if someone else needs it:
<?php
//$url and $data are the same as above
//initialize cURL
$handle = curl_init($url);
//post values
curl_setopt($handle, CURLOPT_POST, true);
curl_setopt($handle, CURLOPT_POSTFIELDS, $data);
//set to return the response
curl_setopt($handle, CURLOPT_RETURNTRANSFER, true);
//execute
$response = (curl_exec( $handle ));
?>