php关于mysql长连接问题

1、当 函数 mysql_connect 的前三个参数（server username password）相同，并且第四个参数（new_link）不传递时候，重复调用 mysql_connect 是会返回相同的连接。

php代码

<?php
$db = mysql_connect('localhost','root','root');
var_dump($db);
$db2 = mysql_connect('localhost','root','root');
var_dump($db2);
sleep(10);

页面打印信息

resource(3) of type (mysql link) resource(3) of type (mysql link) 

mysql连接数

mysql> show full processlist;
+----+------+-----------------+------+---------+------+-------+-----------------------+
| Id | User | Host            | db   | Command | Time | State | Info                  |
+----+------+-----------------+------+---------+------+-------+-----------------------+
| 32 | root | localhost:54408 | NULL | Query   |    0 | NULL  | show full processlist |
| 44 | root | localhost:55278 | NULL | Sleep   |    3 |       | NULL                  |
+----+------+-----------------+------+---------+------+-------+-----------------------+
2 rows in set

2、当函数 mysql_connect 传递了第四个参数（new_link）后，再重复调用它。

php代码

<?php
$db = mysql_connect('localhost','root','root',1);
var_dump($db);
$db2 = mysql_connect('localhost','root','root',1);
var_dump($db2);
sleep(10);

页面打印信息

resource(3) of type (mysql link) resource(5) of type (mysql link) 

mysql连接数

mysql> show full processlist;
+----+------+-----------------+------+---------+------+-------+-----------------------+
| Id | User | Host            | db   | Command | Time | State | Info                  |
+----+------+-----------------+------+---------+------+-------+-----------------------+
| 32 | root | localhost:54408 | NULL | Query   |    0 | NULL  | show full processlist |
| 45 | root | localhost:55320 | NULL | Sleep   |    4 |       | NULL                  |
| 46 | root | localhost:55321 | NULL | Sleep   |    4 |       | NULL                  |
+----+------+-----------------+------+---------+------+-------+-----------------------+

3、mysql_pconnect 持久连接

php代码

<?php
$db = mysql_pconnect('localhost','root','root');
var_dump($db);
$db2 = mysql_pconnect('localhost','root','root');
var_dump($db2);

页面打印信息

resource(3) of type (mysql link persistent) resource(4) of type (mysql link persistent) 

mysql连接数

mysql> show full processlist;
+----+------+-----------------+------+---------+------+-------+-----------------------+
| Id | User | Host            | db   | Command | Time | State | Info                  |
+----+------+-----------------+------+---------+------+-------+-----------------------+
|  1 | root | localhost:55391 | NULL | Query   |    0 | NULL  | show full processlist |
|  2 | root | localhost:55393 | NULL | Sleep   |    5 |       | NULL                  |
+----+------+-----------------+------+---------+------+-------+-----------------------+

4、mysql_pconnect 加上第四个参数（new_link）即可 建立多个 持久连接

php代码

<?php
$db = mysql_pconnect('localhost','root','root',1);
var_dump($db);
$db2 = mysql_pconnect('localhost','root','root',1);
var_dump($db2);

页面打印信息

resource(3) of type (mysql link persistent) resource(4) of type (mysql link persistent) 

mysql连接数

mysql> show full processlist;
+----+------+-----------------+------+---------+------+-------+-----------------------+
| Id | User | Host            | db   | Command | Time | State | Info                  |
+----+------+-----------------+------+---------+------+-------+-----------------------+
|  1 | root | localhost:55391 | NULL | Query   |    0 | NULL  | show full processlist |
|  2 | root | localhost:55393 | NULL | Sleep   |  316 |       | NULL                  |
|  3 | root | localhost:55418 | NULL | Sleep   |    4 |       | NULL                  |
+----+------+-----------------+------+---------+------+-------+-----------------------+
3 rows in set

5、总结：

函数 mysql_pconnetc 创建的 持久化连接 在php脚本结束后，mysql的连接并不会立即结束。什么时候结束，是由mysql自己管理。函数 mysql_colse 不能关闭 mysql_pconnetc 的连接。

函数 mysql_connetc 创建的 连接 在php脚本结束后，mysql的连接也会相应结束。