When using the https protocol you'll have to make sure to set the right context options to use the full "power" of the ssl/tls encryption.
<?php
$url = 'https://secure.example.com/test/1';
$contextOptions = array(
'ssl' => array(
'verify_peer' => true,
'cafile' => __DIR__ . '/cacert.pem',
'verify_depth' => 5,
'CN_match' => 'secure.example.com'
)
);
$sslContext = stream_context_create($contextOptions);
$result = file_get_contents($url, NULL, $sslContext);
?>
More information about those context options can be found at http://php.net/manual/en/context.ssl.php