MySQL in a Nutshell

Name

mysql_ping( )

Synopsis

mysql_ping([connection])

Use this to determine if the current MySQL connection is still open. If it’s not open, the function attempts to reestablish the connection. If the connection is open or reopened, true is returned. If the connection is not open and cannot be reestablished, false is returned. An identifier may be given to ping a different connection.

...
$ping = mysql_ping($connection);
print "Info:  $ping \n";
...

This function is available as of Version 4.3 of PHP.