My database seems to have many open connections despite having no users on httpd.

```
mysql> SHOW PROCESSLIST;
+-------+----------+--------------------+---------------------+---------+------+-------+------------------+
| Id    | User     | Host               | db                  | Command | Time | State | Info             |
+-------+----------+--------------------+---------------------+---------+------+-------+------------------+
| 22865 | rdsadmin | localhost:51066    | mysql               | Sleep   |    8 |       | NULL             |
| 25098 | ubuntu   | 123.45.67.89:48060 | database_name_here! | Sleep   |  350 |       | NULL             |
| 25099 | ubuntu   | 123.45.67.89:48069 | database_name_here! | Sleep   | 3731 |       | NULL             |
| 25126 | ubuntu   | 123.45.67.89:49558 | database_name_here! | Sleep   |  349 |       | NULL             |
| 25161 | ubuntu   | 123.45.67.89:50770 | database_name_here! | Sleep   |  289 |       | NULL             |
| 26583 | ubuntu   | 123.45.67.89:37593 | database_name_here! | Sleep   | 4550 |       | NULL             |
| 29729 | ubuntu   | 123.45.67.89:49280 | database_name_here! | Sleep   |  953 |       | NULL             |
| 29737 | ubuntu   | 123.45.67.89:49489 | database_name_here! | Sleep   |  953 |       | NULL             |
| 29738 | ubuntu   | 123.45.67.89:49490 | database_name_here! | Sleep   |  349 |       | NULL             |
| 29755 | ubuntu   | 123.45.67.89:50674 | database_name_here! | Sleep   | 2751 |       | NULL             |
| 29759 | ubuntu   | 123.45.67.89:50892 | database_name_here! | Sleep   |  600 |       | NULL             |
| 35600 | ubuntu   | 123.45.67.89:49677 | NULL                | Query   |    0 | NULL  | SHOW PROCESSLIST |
+-------+----------+--------------------+---------------------+---------+------+-------+------------------+

```

I don't understand how there are so many connections. I'm using amazon EC2 with RDS, apache/mysql/PHP with PDO. I have persistent connections "on", but I thought this simply cached the connection. It seems somehow 10 connections remain open constantly even though there are 1-2 users on my site at any given time.

What is the cause of this, and how can I fix it? Is this normal behavior, are there a minimum amount of connections that MySQL keeps open to handle different users? I cannot seem to find any information on how to analyze what is going on.