A very efficient way to get mysql dump from remote PHP server.

dump.php

<?php

// Note: Some authentication logics should be here!

// Setup enviroment
header('Content-Disposition: attachment; filename="backup.sql"');
ini_set('display_errors', 1);
ini_set('display_startup_errors', 1);
ini_set('max_execution_time', 0); // disable execution time limit
error_reporting(E_ALL);

// Database information (please fill in your own)
$dbname = '...';
$user = '...';
$pass = '...';
$host = '...';
$port = '...';

// Prepare proc context
$descriptorspec = [
    0 => array("pipe", "r"), // stdin is a pipe that the child will read from
    1 => array("pipe", "w"), // stdout is a pipe that the child will write to
    2 => array("pipe", "w")  // stderr is a pipe that the child will write to
];
flush();

// Run the mysqldump command then passthrough the output
$cmd = "mysqldump --user={$user} --password={$pass} --host={$host} --port={$port} {$dbname}";
$process = proc_open($cmd, $descriptorspec, $pipes, realpath('./'), array());
if (is_resource($process)) {
    while ($s = fgets($pipes[1])) {
        print $s;
        flush();
    }
}