适配器模式，可以将截然不同的函数接口封装成统一的API；
应用举例，PHP的数据库操作有Mysql、Mysqli、pdo三种，可以用适配器模式统一成一致，类似的场景还有cache适配器，将memcache、redis，file，apc等不同的缓存函数统一成一致。
IDatabase.php
<?<span>php
namespace Baobab;
</span><span>interface</span><span> IDatabase{
</span><span>function</span> connect(<span>$host</span>, <span>$user</span>, <span>$passwd</span>, <span>$dbname</span><span>);
</span><span>function</span> query(<span>$sql</span><span>);
</span><span>function</span> fetch_result(<span>$result</span><span>);
</span><span>function</span><span> close();
}</span>Mysqli.php
<?<span>php
namespace Baobab\Database;
</span><span>use</span><span> Baobab\IDatabase;
</span><span>class</span> Mysqli <span>implements</span><span> IDatabase{
</span><span>protected</span> <span>$conn</span><span>;
</span><span>function</span> connect(<span>$host</span>, <span>$user</span>, <span>$passwd</span>, <span>$dbname</span><span>){
</span><span>$conn</span> = <span>mysqli_connect</span>(<span>$host</span>, <span>$user</span>, <span>$passwd</span>, <span>$dbname</span><span>);
mysqli_set_charset(</span><span>$conn</span>, 'utf8'<span>);
</span><span>$this</span>->conn = <span>$conn</span><span>;
}
</span><span>function</span> query(<span>$sql</span><span>) {
</span><span>return</span> <span>mysqli_query</span>(<span>$this</span>->conn, <span>$sql</span><span>);
}
</span><span>function</span> fetch_result(<span>$result</span><span>){
</span><span>return</span> mysqli_fetch_all(<span>$result</span><span>);
}
</span><span>function</span><span> close() {
</span><span>mysqli_close</span>(<span>$this</span>-><span>conn);
}
}</span>Pdo.php
<?<span>php
namespace Baobab\Database;
</span><span>use</span><span> Baobab\IDatabase;
</span><span>class</span> Pdo <span>implements</span><span> IDatabase{
</span><span>protected</span> <span>$conn</span><span>;
</span><span>function</span> connect(<span>$host</span>, <span>$user</span>, <span>$passwd</span>, <span>$dbname</span><span>){
</span><span>$conn</span> = <span>new</span> \PDO("mysql:dbname=<span>$dbname</span>;host=<span>$host</span>", <span>$user</span>, <span>$passwd</span><span>);
</span><span>$this</span>->conn = <span>$conn</span><span>;
}
</span><span>function</span> query(<span>$sql</span><span>){
</span><span>return</span> <span>$this</span>->conn->query(<span>$sql</span><span>);
}
</span><span>function</span> fetch_result(<span>$result</span><span>){
}
</span><span>function</span><span> close() {
</span><span>unset</span>(<span>$this</span>-><span>conn);
}
}</span>index.php
<span>$db</span> = <span>new</span><span> Baobab\Database\Mysqli();
</span><span>$db</span>->connect('127.0.0.1', 'root', '', 'test'<span>);
</span><span>$res</span> = <span>$db</span>->query('select * from ha_cl'<span>);
</span><span>print_r</span>(<span>$db</span>->fetch_result(<span>$res</span><span>));
</span><span>$db</span>->close();
