Question

How to Solve MySQL Warning: mysql_query(): 5 is not a valid MySQL-Link resource

Answer 1

You just use: mysql_close($connection); somewhere in your code and continue to work on your database. 
Move mysql_close($connection); to the line after you finish working on your database.

Example:

$connection = mysql_connect(...);
mysql_select_db(...);
SELECT ...
INSERT INTO ...

mysql_close($connection);

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