mysql_query

mysql_pconnect

[edit] Last updated: Fri, 24 May 2013

mysql_ping

(PHP 4 >= 4.3.0, PHP 5)

mysql_ping — Проверяет соединение с сервером и пересоединяется при необходимости

Описание

bool mysql_ping ([ resource $link_identifier = NULL ] )

Проверяет работает ли соединение с сервером. Если оно утеряно, автоматически предпринимается попытка пересоединения. Эта функция может быть использована в скриптах, работающих на протяжении долгого времени.

Замечание:
Автоматическое восстановление соединения по умолчанию отключено в версиях MySQL > = 5.0.3.

Список параметров

link_identifier: Соединение MySQL. Если идентификатор соединения не был указан, используется последнее соединение, открытое mysql_connect(). Если такое соединение не было найдено, функция попытается создать таковое, как если бы mysql_connect() была вызвана без параметров. Если соединение не было найдено и не смогло быть создано, генерируется ошибка уровня E_WARNING.

Возвращаемые значения

Возвращает TRUE, если соединение в рабочем состоянии и FALSE в противном случае.

Примеры

Пример #1 Пример использования mysql_ping()


<?php
set_time_limit(0);

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

/* Подразумевается что этот запрос будет выполняться достаточно долго */
$result = mysql_query($sql);
if (!$result) {
    echo 'Запрос #1 не удался, выходим.';
    exit;
}

/* Проверяем что соединение еще работает, если нет, соединяемся заново */
if (!mysql_ping($conn)) {
    echo 'Соединение потеряно, выходим после запроса #1';
    exit;
}
mysql_free_result($result);

/* Соединение еще работает, выполняем еще один запрос */
$result2 = mysql_query($sql2);
?>

Смотрите также

mysql_thread_id() - Возвращает идентификатор текущего потока
mysql_list_processes() - Возвращает список процессов MySQL

mysql_query

mysql_pconnect

[edit] Last updated: Fri, 24 May 2013

add a note User Contributed Notes mysql_ping - [8 notes]

down

alext at marketdream dot com dot mx ¶

3 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.

down

luky37 ¶

4 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).

down

miro dot dietiker at md-systems dot ch ¶

5 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...

down

dustin hawkins ¶

6 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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cybot2000 at yahoo dot de ¶

8 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.

down

-1

Doug ¶

3 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.

down

-1

oscar at bitagenda dot com ¶

5 years ago


Very confusing description.

... If it has gone down, an automatic reconnection is attempted

 (But the function returns only true or false, so if you have variable say $link = connection resource, it will be an invalid resource)



Then ...

... Note:  Since MySQL 5.0.13, automatic reconnection feature is disabled.



OK, if it returns false, I have the chance to reconnect updating my resource variable

$link = reconnect



But I did called the function with $link to do the check, so ...

If no such link is found, it will try to create one as if mysql_connect() was called with no arguments (this are  different arguments than automatic reconnection, doesn't it? I think, automatic reconnecting, say to $link, would be with its own arguments previously used to create the connection)



So bad decision about automatic recconection feature disabled ...



At least the function should have the param by reference, so in case it reconnects with a new link_identifier.



bool mysql_ping ( &[resource $link_identifier] )



Or a return value of link_identifier, not true.



if ($link=mysql_ping($link)) {...} else { whatever }

down

-1

vinicius at teracom dot com dot br ¶

9 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.

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