mysqli::close()

(PHP 5, PHP 7)

关闭先前打开的数据库连接

说明

面向对象风格
mysqli::close(void): bool

过程化风格
mysqli_close(mysqli$link): bool

关闭先前打开的数据库连接

参数

$link

仅以过程化样式：由mysqli_connect()或mysqli_init()返回的链接标识。

返回值

成功时返回TRUE，或者在失败时返回FALSE。

范例

See mysqli_connect().

参见

• mysqli::__construct() Open a new connection to the MySQL server
• mysqli_init() 初始化 MySQLi 并返回一个资源类型的值，这个值可以作为 mysqli_real_connect()函数的传入参数
• mysqli_real_connect() 建立一个 MySQL 服务器连接

Note with Francis' example, using the function name link() will throw an error at runtime as it is already a function within the language. see: http://php.net/manual/en/function.link.php

Since a lot of manual examples recommend to use a variable to initiate your connection, it is interesting to know that mysqli_close() will unset that variable, causing further connection attempts to fail.
ex:
$link = mysqli_connect($host, $user, $pw);
if ($link) {
  // Database is reachable
  mysqli_close($link);
}
if ($link) {
  // Database unreachable because $link = NULL
}
Easiest solution for me is to initiate connection through a function.
ex:
function link() {
  global $host;
  global $user;
  global $pw;
  global $link;
  $link = mysqli_connect($host, $user, $pw);
}
link();
// Database is reachable
mysqli_close($link)
link();
// Database is reachable
mysqli_close($link)

I've had situations where database connections appeared to persist following php execution. So, now, my __destructor function explicitly contains a $cxn->close(). It hurts nothing, and helps avoid memory leaks.