PHP mysqli如何连接MySQL数据库

在学习1. 开启PHP的API支持

（1）首先修改您的php.ini的配置文件。
查找下面的语句：
;extension=php_mysqli.dll
将其修改为：
extension=php_mysqli.dll

（2）重新启动Apache/IIS，即可。

（3）说明：PHP需要单独的文件来支持这个扩展库，一般在PHP目录下的ext目录里能找到php_mysqli.dll文件（PHP

2.PHP mysqli身份证

mysqli是“MySQL, Improved”的缩写，该扩展仅适用于PHP 5。它能用于MySQL 4.1.1和更高版本。该扩展完全支持MySQL 5.1中采用的鉴定协议，也支持预处理语句和多语句API。此外，该扩展还提供了先进的、面向对象的编程接口。

3. mysqli预定义类

mysqli

表达了 PHP 和 MySQL 数据库之间的连接。 

构造函数

mysqli - 构造一个新的PHP mysqli对象

方法

autocommit - 打开或关闭自动提交的数据库选项
change_user - 改变指定的数据库连接的用户
character_set_name - 返回数据库连接的默认字符集
close - 关闭一个之前打开的连接
commit - 提交当前事务
connect - 打开一个到 MySQL 数据库服务器的新连接
debug - 执行排错操作
dump_debug_info - 取得排错信息
get_client_info - 返回客户端版本
get_host_info - 返回连接使用的类型
get_server_info - 返回 MySQL 服务器的版本
get_server_version - 返回 MySQL 服务器的版本
init - 初始化PHP mysqli对象
info - 取得最近执行的查询的信息
kill - 要求服务器停止一个 mysql 线程
multi_query - 执行多个查询
more_results - check if more results exist from currently executed multi-query
next_result - reads next result from currently executed multi-query
options - set options
ping - pings a server connection or reconnects if there is no connection
prepare - prepares a SQL query
query - performs a query
real_connect - attempts to open a connection to MySQL database server
escape_string - escapes special characters in a string for use in a SQL statement, taking into account the current charset of the connection
rollback - rolls back the current transaction
select_db - selects the default database
set_charset - sets the default client character set
ssl_set - sets ssl parameters
stat - gets the current system status
stmt_init- initializes a statement for use with mysqli_stmt_prepare
store_result - transfers a resultset from last query
thread_safe - returns whether thread safety is given or not
use_result - transfers an unbuffered resultset from last query

属性

affected_rows - gets the number of affected rows in a previous MySQL operation
client_info - returns the MySQL client version as a string
client_version - returns the MySQL client version as an integer
errno - returns the error code for the most recent function call
error - returns the error string for the most recent function call
field_count - returns the number of columns for the most recent query
host_info - returns a string representing the type of connection used
info - retrieves information about the most recently executed query
insert_id - returns the auto generated id used in the last query
protocol_version - returns the version of the MySQL protocol used
server_info - returns a string that represents the server version number
server_version - returns the version number of the server as an integer
sqlstate - returns a string containing the SQLSTATE error code for the last error
thread_id - returns the thread ID for the current connection
warning_count - returns the number of warnings generated during execution of the previous SQL statement

 4. 基本语法

<ol class="dp-xml">
<li class="alt"><span><strong><font color="#006699"><span class="tag"></span><span class="tag-name">php</span></font></strong><span>   </span></span></li>
<li class=""><span>      </span></li>
<li class="alt"><span>    /* Connect to a MySQL server  连接数据库服务器 */   </span></li>
<li class="">
<span>    $</span><span class="attribute"><font color="#ff0000">link</font></span><span> = </span><span class="attribute-value"><font color="#0000ff">mysqli_connect</font></span><span>(   </span>
</li>
<li class="alt"><span>                'localhost',  /* The host to connect to 连接MySQL地址 */   </span></li>
<li class=""><span>                'user',      /* The user to connect as 连接MySQL用户名 */   </span></li>
<li class="alt"><span>                'password',  /* The password to use 连接MySQL密码 */   </span></li>
<li class=""><span>                'world');    /* The default database to query 连接数据库名称*/   </span></li>
<li class="alt"><span>      </span></li>
<li class=""><span>    if (!$link) {   </span></li>
<li class="alt"><span>       printf("Can't connect to MySQL Server. Errorcode: %s ", mysqli_connect_error());   </span></li>
<li class=""><span>       exit;   </span></li>
<li class="alt"><span>    }   </span></li>
<li class=""><span>      </span></li>
<li class="alt"><span>    /* Send a query to the server 向服务器发送查询请求*/   </span></li>
<li class="">
<span>    if ($</span><span class="attribute"><font color="#ff0000">result</font></span><span> = </span><span class="attribute-value"><font color="#0000ff">mysqli_query</font></span><span>($link, 'SELECT Name, Population FROM City ORDER BY Population DESC LIMIT 5')) {   </span>
</li>
<li class="alt"><span>      </span></li>
<li class=""><span>        print("Very large cities are: ");   </span></li>
<li class="alt"><span>      </span></li>
<li class=""><span>        /* Fetch the results of the query 返回查询的结果 */   </span></li>
<li class="alt">
<span>        while( $</span><span class="attribute"><font color="#ff0000">row</font></span><span> = </span><span class="attribute-value"><font color="#0000ff">mysqli_fetch_assoc</font></span><span>($result) ){   </span>
</li>
<li class=""><span>            printf("%s (%s) ", $row['Name'], $row['Population']);   </span></li>
<li class="alt"><span>        }   </span></li>
<li class=""><span>      </span></li>
<li class="alt"><span>        /* Destroy the result set and free the memory used for it 结束查询释放内存 */   </span></li>
<li class=""><span>        mysqli_free_result($result);   </span></li>
<li class="alt"><span>    }   </span></li>
<li class=""><span>      </span></li>
<li class="alt"><span>    /* Close the connection 关闭连接*/   </span></li>
<li class=""><span>    mysqli_close($link);   </span></li>
<li class="alt">
<span>    </span><span class="tag"><strong><font color="#006699">?></font></strong></span><span> </span>
</li>
</ol>

以上所描写的解决办法能够帮助我们轻松解决PHP mysqli连接数据库的问题。