mysql_ping

(PHP 4 >= 4.3.0, PHP 5)

mysql_ping — pinga uma conexão com o servidor ou reconecta se não houver conexão

Descrição

bool mysql_ping ([ resource $link_identifier ] )

Confere se uma conexão com um servidor esta funcionando ou não. Se ela tiver caído, tenta realizar uma conexão automatica. Esta função pode ser usada em scripts que permanecem inativos por um longo tempo, para conferir se o servidor fechou ou não a conexão e reconectar se necessário.

Nota: Desde o MySQL 5.0.13, o recurso de automática reconexão está desabilitada.

Parâmetros

link_identifier: A conexão MySQL. se o identificador de conexão não for especificado, a ultima conexão aberta por mysql_connect() é assumida. Se uma conexão assim não for encontrada, ela irá tentar criar uma como se a função mysql_connect() fosse chamada sem argumentos. Se uma conexão não for encontrada ou estabelecida, um aviso de nível de erro E_WARNING é gerado.

Valor Retornado

Retorna TRUE se a conexão com o servidor MySQL esta funcionando, se não retorna FALSE.

Exemplos

Exemplo #1 Exemplo mysql_ping()


<?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);
?>

Veja Também

mysql_thread_id() - Returna o ID da thread atual
mysql_list_processes() - Lista os processos MySQL

mysql_query

mysql_pconnect

Last updated: Fri, 06 Nov 2009

add a note User Contributed Notes
mysql_ping

alext at marketdream dot com dot mx
29-Sep-2009 03:28


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.

luky37
03-Feb-2009 07:15


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).

oscar at bitagenda dot com
02-Oct-2007 11:10


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 }

miro dot dietiker at md-systems dot ch
31-Aug-2007 06:32


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...

dustin hawkins
31-Jul-2006 07:32


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....



?>

cybot2000 at yahoo dot de
25-May-2005 11:44


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.

vinicius at teracom dot com dot br
16-Mar-2004 03:35


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.

add a note

mysql_query

mysql_pconnect

Last updated: Fri, 06 Nov 2009