function make_code($t=20){
	$ranges[1][1] = 65;
	$ranges[1][2] = 90;
	
	$ranges[2][1] = 97;
	$ranges[2][2] = 122;
	
	$ranges[3][1] = 48;
	$ranges[3][2] = 57;

	$code = "";
	for($i=0; $i < $t; $i++){
		$range = rand(1,2);
		$code .= chr(rand($ranges[$range][1], $ranges[$range][2]));
	}
	return $code;
}