PHP database operation mysqli

<code><span>$server</span> = <span>"127.0.0.1"</span>;
<span>$username</span> = <span>"username"</span>;
<span>$pass</span> = <span>"password"</span>;
<span>$con</span> = new mysqli(<span>$server</span>,<span>$username</span>,<span>$pass</span>[,<span>$db_name</span>]);
///创建一个数据库链接,如果带上后面参数 <span>$db_name</span> 创建一个到数据库<span>$db_name</span>的链接,如果后面不带参数,创建一个到server的链接,在后面可以使用 <span>$con</span> -> select_db(<span>$db_name</span>);来选择数据表</code>

<code><span>try</span>{
    <span>$con</span> -> query(<span>$create_db</span>);
}<span>catch</span> (<span>exception</span><span>$e</span>){
}
<span>$con</span> -> select_db(<span>"nwpu"</span>);
<span>///使用try 可以避免重复创建数据库报错,</span></code>

<code>$table = "<span><span>create</span><span>table</span> name(<span>".
        "</span><span>first</span><span>varchar</span>(<span>20</span>) <span>PRIMARY</span><span>KEY</span>,<span>".
        "</span>sec <span>VARCHAR</span>(<span>20</span>)<span>".
    "</span>)<span>";
$con -> query($table);
///使用query执行sql语句</span></span></code>

<code><span>$con</span> -> <span>close</span>();</code>