mysql_ping

(PHP 4 >= 4.3.0, PHP 5)

mysql_pingPing 服务器连接的状态,如果没有连接则重新连接

警告

本扩展自 PHP 5.5.0 起已废弃,并在自 PHP 7.0.0 开始被移除。应使用 MySQLiPDO_MySQL 扩展来替换之。参见 MySQL:选择 API 指南来获取更多信息。用以替代本函数的有:

说明

mysql_ping(resource $link_identifier = NULL): bool

检查到服务器的连接是否正常。如果断开,则自动尝试连接。本函数可用于空闲很久的脚本来检查服务器是否关闭了连接,如果有必要则重新连接上。。

注意:

从 MySQL 版本 5.0.3 开始,默认情况下不启用自动重新连接功能。

参数

link_identifier

MySQL 连接。如不指定连接标识,则使用由 mysql_connect() 最近打开的连接。如果没有找到该连接,会尝试不带参数调用 mysql_connect() 来创建。如没有找到连接或无法建立连接,则会生成 E_WARNING 级别的错误。

返回值

如果到服务器的连接可用则,返回 true,否则返回 false

示例

示例 #1 mysql_ping() 示例

<?php
set_time_limit
(0);

$conn = mysql_connect('localhost', 'mysqluser', 'mypass');
$db = mysql_select_db('mydb');

/* Assuming this query will take a long time */
$result = mysql_query($sql);
if (!
$result) {
echo
'Query #1 failed, exiting.';
exit;
}

/* Make sure the connection is still alive, if not, try to reconnect */
if (!mysql_ping($conn)) {
echo
'Lost connection, exiting after query #1';
exit;
}
mysql_free_result($result);

/* So the connection is still alive, let's run another query */
$result2 = mysql_query($sql2);
?>

参见

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User Contributed Notes 7 notes

up
3
cybot2000 at yahoo dot de
19 years ago
It should be noted that mysql_ping() seems to reset the error message on the server.
I used it to check whether the connection was still alive before reading the error message via mysql_error() and it always returned an empty string. Upon removing the connection check everything worked.
up
3
alext at marketdream dot com dot mx
15 years ago
mysql_ping() is really helpful when you have this annoying error:

MYSQL Error 2006 Server has gone away

For CI users:
In 1.7.2 version of codeigniter, there is a function

$this->db->reconnect()

that uses mysql_ping() to reestablish the timed out connection.

This function is specially useful when developing social media sites that uses hundreds of connections to the db such asinserting or selecting.
up
3
dustin hawkins
18 years ago
When using the mysql_ping command under php 5.1.2 and mysql 5.0, I was having problems with the auto-reconnect "feature", mainly that when the connection was severed, a mysql_ping would not automatically re-establish the connection to the database.

The connection to the DB is dropped when the time without a query excedes the wait_timeout value in my.cnf. You can check your wait_timeout by running the query "SHOW VARIABLES;"

If you're having problems auto-reconnecting when the connection is dropped, use this code:

<?php

$conn
= mysql_connect('localhost','user','pass');
mysql_select_db('db',$conn);

if (!
mysql_ping ($conn)) {
  
//here is the major trick, you have to close the connection (even though its not currently working) for it to recreate properly.
  
mysql_close($conn);
  
$conn = mysql_connect('localhost','user','pass');
  
mysql_select_db('db',$conn);
}

//run queries knowing that your connection is alive....

?>
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2
miro dot dietiker at md-systems dot ch
17 years ago
When checking if a $resource works...
be prepared that mysql_ping returns NULL as long as $resource is no correct mysql resource.
<?php
$resource
=NULL;
var_dump = @mysql_ping($resource);
# showing NULL
?>
This could be used to decide of a current $resource is a mysql or a mysqli connection when nothing else is available to do that...
up
2
Doug
14 years ago
This function *does not* attempt to reconnect at this time.  It only tells you whether or not you currently *are* connected.

To actually reconnect, you will have to implement this yourself in a wrapper class.
up
2
vinicius at teracom dot com dot br
20 years ago
Is important to remember that if your first connection to mysql don't works, mysql_ping will always return true! So, if you want to check if mysql is connected, first of all you must check if mysql_connect do not returns false and then you can begin to check mysql_ping.
up
-3
luky37
15 years ago
If you get 'error 2006: MySQL server has gone away' messages when running (really) long scripts, mysql_ping will help detecting the loss of the db-connection. This can happen, when 'wait timeout' is reached (MySQL default is 8 hours).
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