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 mysqli_ping    (PHP 5) mysqli_ping     (no version information, might be only in CVS) mysqli->ping -- 
     Pings a server connection, or tries to reconnect if the connection has gone down
     DescriptionProcedural style: bool  mysqli_ping ( mysqli link ) Object oriented style (method): class  mysqli {  bool  ping ( void  ) } 
     Checks whether the connection to the server is working. If it has gone
     down, and global option mysqli.reconnect is enabled
     an automatic reconnection is attempted.
     
     This function can be used by clients that remain idle for a long while,
     to check whether the server has closed the connection and reconnect if
     necessary.
     返回值如果成功则返回 TRUE,失败则返回 FALSE。 例例子 1. Object oriented style 
<?php $mysqli = new mysqli("localhost", "my_user", "my_password", "world");
  /* check connection */ if (mysqli_connect_errno()) {     printf("Connect failed: %s\n", mysqli_connect_error());     exit(); }
  /* check if server is alive */ if ($mysqli->ping()) {     printf ("Our connection is ok!\n"); } else {     printf ("Error: %s\n", $mysqli->error); }
  /* close connection */ $mysqli->close(); ?>
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 例子 2. Procedural style 
<?php $link = mysqli_connect("localhost", "my_user", "my_password", "world");
  /* check connection */ if (mysqli_connect_errno()) {     printf("Connect failed: %s\n", mysqli_connect_error());     exit(); }
  /* check if server is alive */ if (mysqli_ping($link)) {     printf ("Our connection is ok!\n"); } else {     printf ("Error: %s\n", mysqli_error($link)); }
  /* close connection */ mysqli_close($link); ?>
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 上例将输出: 
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