Can you join 2 databases in mysql using php?

Can you join 2 databases in mysql using php?

Is it possible to join 2 different databases in mysql using php?
for instance:
$sql = "SELECT * FROM db1.table LEFT JOIN db2.table USING (id)";
$result = mysql_query($sql);
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I know how to create multiple new different database connections using
php. But I'm unable to figure out if it's possible to acutally join two
different databases in mysql using php in one query.