使用方法：$s=make_password(长度); 
如：$s=make_password(8); //将会随机生成一串8位数的字符串。

//取得随机数(混合)，字母大小写加数字
function make_password($pw_length){
	$low_ascii_bound=50;
	$upper_ascii_bound=122;
	$notuse=array(58,59,60,61,62,63,64,73,79,91,92,93,94,95,96,108,111);
	while($i<$pw_length)
	{
		mt_srand((double)microtime()*1000000);
		$randnum=mt_rand($low_ascii_bound,$upper_ascii_bound);
		if(!in_array($randnum,$notuse))
		{
			$password1=$password1.chr($randnum);
			$i++;
		}
	}
	return $password1;
}

//取得随机数(数字)
function no_make_password($pw_length){
	$low_ascii_bound=48;
	$upper_ascii_bound=57;
	$notuse=array(58,59,60,61,62,63,64,73,79,91,92,93,94,95,96,108,111);
	while($i<$pw_length)
	{
		mt_srand((double)microtime()*1000000);
		$randnum=mt_rand($low_ascii_bound,$upper_ascii_bound);
		if(!in_array($randnum,$notuse))
		{
			$password1=$password1.chr($randnum);
			$i++;
		}
	}
	return $password1;
}