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.
mysql_ping
(PHP 4 >= 4.3.0, PHP 5)
mysql_ping — Ping a server connection or reconnect if there is no connection
Warning
This extension is deprecated as of PHP 5.5.0, and will be removed in the future. Instead, the MySQLi or PDO_MySQL extension should be used. See also MySQL: choosing an API guide and related FAQ for more information. Alternatives to this function include:
說明
bool mysql_ping
([ resource
$link_identifier = NULL
] )Checks whether or not the connection to the server is working. If it has gone down, an automatic reconnection is attempted. This function can be used by scripts that remain idle for a long while, to check whether or not the server has closed the connection and reconnect if necessary.
Note:
Automatic reconnection is disabled by default in versions of MySQL >= 5.0.3.
參數
-
link_identifier -
MySQL 的連接識別符。如果沒有指定，預設使用最後被 mysql_connect() 打開的連接。如果沒有找到該連接，函式會嘗試呼叫 mysql_connect() 建立連接並使用它。如果發生意外，沒有找到連接或無法建立連接，系統發出
E_WARNING級別的警告信息。
回傳值
Returns TRUE if the connection to the server MySQL server is working,
otherwise FALSE.
範例
Example #1 A mysql_ping() example
<?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);
?>
add a note
User Contributed Notes 7 notes
cybot2000 at yahoo dot de ¶
18 years ago
alext at marketdream dot com dot mx ¶
14 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.
dustin hawkins ¶
17 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....
?>
miro dot dietiker at md-systems dot ch ¶
16 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...
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.
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.
