If you want to mimic HTML form POST action, you can use cURL.
// POST data in array
$post = [
'a' => 'apple',
'b' => 'banana'
];
// Create a new cURL resource with URL to POST
$ch = curl_init('http://www.example.com');
// We set parameter CURLOPT_RETURNTRANSFER to read output
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
// Let's pass POST data
curl_setopt($ch, CURLOPT_POSTFIELDS, $post);
// We execute our request, and get output in a $response variable
$response = curl_exec($ch);
// Close the connection
curl_close($ch);