为什么mysql_connect（）返回NULL？

Question

I'm running my program on PHP 5.5.24,when I simply use :

$dblink = mysql_connect($dbhost, $dbuser, $dbpass);

But the function return NULL, I try to use mysql_error() to find out what's wrong, but it also returns an empty string. I know mysql_* is deprecated after 5.5.0, but I'm dealing with a very old repository. It will cost a lot of time to change into mysqli. The function suppose to refurn false if the connection failed, no NULL. Why does it happen?

Answer 1

seems it can return null, search the source for cases when it can happen