mysql_ping

(PHP 4 >= 4.3.0, PHP 5)

mysql_ping서버 접속을 검사하고 접속이 없으면 재접속한다

설명

bool mysql_ping ([ resource $link_identifier ] )

서버로의 접속이 정상적으로 동작하는지 점검한다. 접속이 종료되었다면 자동으로 재접속을 시도한다. 이 함수는 스크립트에서 사용된 이후 오랜 시간동안 멈추어 있을 때때, 접속이 종료되지 않았는지 점검하고 필요시에는 재접속을 하는 용도로 사용된다.

Note:

MySQL 5.0.13부터, 자동 재접속 기능은 사라졌습니다.

인수

link_identifier

MySQL 연결. 지정하지 않으면 mysql_connect()로 연 마지막 연결을 사용합니다. 연결이 없으면, 인수 없이 mysql_connect()를 호출하여 연결을 만듭니다. 연결이 성립되지 않으면 E_WARNING 등급의 오류를 생성합니다.

반환값

MySQL 서버와의 접속이 정상적이면 TRUE를 그렇지 않다면 FALSE를 반환한다.

예제

Example #1 mysql_ping() 예제

<?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);
?>

참고

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User Contributed Notes 7 notes

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4
alext at marketdream dot com dot mx
10 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.
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3
cybot2000 at yahoo dot de
15 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.
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3
dustin hawkins
14 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
12 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...
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2
vinicius at teracom dot com dot br
16 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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0
Doug
10 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.
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-5
luky37
11 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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