PHP如何连接MySQL数据库

任卓 · 发表于 2023-5-26 16:20:04

首先我们看一下初始版本的数据库文件application-config-database.php：
$active_group = &#39;default&#39;;
$query_builder = TRUE;

$db[&#39;default&#39;] = array(
&#39;dsn&#39; => &#39;&#39;,
&#39;hostname&#39; => &#39;localhost&#39;,
&#39;username&#39; => &#39;&#39;,
&#39;password&#39; => &#39;&#39;,
&#39;database&#39; => &#39;&#39;,
&#39;dbdriver&#39; => &#39;mysqli&#39;,
&#39;dbprefix&#39; => &#39;&#39;,
&#39;pconnect&#39; => FALSE,
&#39;db_debug&#39; => (ENVIRONMENT !== &#39;production&#39;),
&#39;cache_on&#39; => FALSE,
&#39;cachedir&#39; => &#39;&#39;,
&#39;char_set&#39; => &#39;utf8&#39;,
&#39;dbcollat&#39; => &#39;utf8_general_ci&#39;,
&#39;swap_pre&#39; => &#39;&#39;,
&#39;encrypt&#39; => FALSE,
&#39;compress&#39; => FALSE,
&#39;stricton&#39; => FALSE,
&#39;failover&#39; => array(),
&#39;save_queries&#39; => TRUE
);
只需简单配置以下几个地方，即可连接数据库：
&#39;hostname&#39; => &#39;localhost&#39;,
&#39;username&#39; => &#39;&#39;,
&#39;password&#39; => &#39;&#39;,
&#39;database&#39; => &#39;&#39;,
&#39;dbdriver&#39; => &#39;mysqli&#39;,
&#39;dbprefix&#39; => &#39;&#39;,
属性如下所示：

属性名	属性含义
hostname	数据库地址
username	用户名称，初始为‘root’
password	连接密码，初始为‘root’
database	数据库名称
dbdriver	数据库类型
dbprefix	数据库前缀

当连接多个数据库时，可如下操作，删除之前的一维数组，增加二维数组，通过改变二维数组的第一列访问不同的数据库，默认为‘default’，我们可以增加自定义的名称，如‘db2’：
$active_group = &#39;default&#39;;
$query_builder = TRUE;

      $db[&#39;default&#39;][&#39;hostname&#39;] = &#39;localhost&#39;;
      $db[&#39;default&#39;][&#39;username&#39;] = &#39;&#39;;
      $db[&#39;default&#39;][&#39;password&#39;] = &#39;&#39;;
      $db[&#39;default&#39;][&#39;database&#39;] = &#39;&#39;;
      $db[&#39;default&#39;][&#39;dbdriver&#39;] = &#39;mysqli&#39;;
      $db[&#39;default&#39;][&#39;dbprefix&#39;] = &#39;&#39;;
      $db[&#39;default&#39;][&#39;pconnect&#39;] = FALSE;
      $db[&#39;default&#39;][&#39;db_debug&#39;] = (ENVIRONMENT !== &#39;production&#39;);
      $db[&#39;default&#39;][&#39;cache_on&#39;] = FALSE;
      $db[&#39;default&#39;][&#39;cachedir&#39;] = &#39;&#39;;
      $db[&#39;default&#39;][&#39;char_set&#39;] = &#39;utf8&#39;;
      $db[&#39;default&#39;][&#39;dbcollat&#39;] = &#39;utf8_general_ci&#39;;
      $db[&#39;default&#39;][&#39;swap_pre&#39;] = &#39;&#39;;
      $db[&#39;default&#39;][&#39;encrypt&#39;] = FALSE;
      $db[&#39;default&#39;][&#39;compress&#39;] = FALSE;
$db[&#39;default&#39;][&#39;stricton&#39;] = FALSE;
$db[&#39;default&#39;][&#39;failover&#39;] = array();
$db[&#39;default&#39;][&#39;save_queries&#39;] = TRUE;

$db[&#39;db2&#39;][&#39;hostname&#39;] = &#39;localhost&#39;;
      $db[&#39;db2&#39;][&#39;username&#39;] = &#39;&#39;;
      $db[&#39;db2&#39;][&#39;password&#39;] = &#39;&#39;;
      $db[&#39;db2&#39;][&#39;database&#39;] = &#39;&#39;;
      $db[&#39;db2&#39;][&#39;dbdriver&#39;] = &#39;mysqli&#39;;
      $db[&#39;db2&#39;][&#39;dbprefix&#39;] = &#39;&#39;;
      $db[&#39;db2&#39;][&#39;pconnect&#39;] = FALSE;
      $db[&#39;db2&#39;][&#39;db_debug&#39;] = (ENVIRONMENT !== &#39;production&#39;);
      $db[&#39;db2&#39;][&#39;cache_on&#39;] = FALSE;
      $db[&#39;db2&#39;][&#39;cachedir&#39;] = &#39;&#39;;
      $db[&#39;db2&#39;][&#39;char_set&#39;] = &#39;utf8&#39;;
      $db[&#39;db2&#39;][&#39;dbcollat&#39;] = &#39;utf8_general_ci&#39;;
      $db[&#39;db2&#39;][&#39;swap_pre&#39;] = &#39;&#39;;
      $db[&#39;db2&#39;][&#39;encrypt&#39;] = FALSE;
      $db[&#39;db2&#39;][&#39;compress&#39;] = FALSE;
$db[&#39;db2&#39;][&#39;stricton&#39;] = FALSE;
$db[&#39;db2&#39;][&#39;failover&#39;] = array();
$db[&#39;db2&#39;][&#39;save_queries&#39;] = TRUE;
在控制器中声明连接变量‘$db_connect1’，如果连接第二个数据库，可增加变量声明，如‘$db_connect2’：
var $db_connect1;
连接数据库：
$this->db_connect1 = $this->load->database(&#39;default&#39;, TRUE);
如果连接第二个数据库，如下，需改变连接变量‘db_connect2’和连接库‘db2’：
$this->db_connect2 = $this->load->database(&#39;db2&#39;, TRUE);

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PHP如何连接MySQL数据库

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