Maintain $dbh (database handle) across all php files

Question

How many ways are there to maintain $dbh (database handle) across all php files, so that once $dbh created, I can query and update database from any php file and any time, witho

Answer 1

In the file that creates $dbh, put

global $dbh;
...
$dbh = new DatabaseClass();
$dbh->example_login("user","pass");
...

In every file and function that wants to use $dbh, put

global $dbh;
...
$result = $dbh->query("SELECT * FROM XYZ");
...

at the start to mark $dbh as global. You could also use a singleton type pattern, although this is considered bad practice in PHP.