Sending POST Request from server

‘wp_remote_post’ is the function you’re searching for.

$response = wp_remote_post( $url, array(
    'method' => 'POST',
    'timeout' => 45,
    'redirection' => 5,
    'httpversion' => '1.0',
    'blocking' => true,
    'headers' => array(),
    'body' => array( 'param1' => 'value1' ),
    'cookies' => array()
    )
);

if ( is_wp_error( $response ) ) {
   $error_message = $response->get_error_message();
   echo "Something went wrong: $error_message";
} else {
   echo 'Response:<pre>';
   print_r( $response );
   echo '</pre>';
}