这应该做你想要的，我有一个需要相同的api。

This should do what you want, I had an api that required the same thing.

$vars = array('foo' => array('x','y'));
$query = http_build_query($vars, null, '&');
$string = preg_replace('/%5B(?:[0-9]|[1-9][0-9]+)%5D=/', '=', $query); //foo=x&foo=y