策略模式：
将一组特定的行为和算法封装成类，以适应某些特定的上下文环境；
实际应用举例，假如一个电商网站系统，针对男性女性用户要各自跳转到不同的商品类目，并且所有广告位展示不同的广告。
UserStrategy.php
<?<span>php
namespace Baobab;
</span><span>interface</span><span> UserStrategy{
</span><span>function</span><span> showAd();
</span><span>function</span><span> showCategory();
}
</span>?>FemaleUserStrategy.php
<?<span>php
namespace Baobab;
</span><span>class</span> FemaleUserStrategy <span>implements</span><span> UserStrategy{
</span><span>function</span><span> showAd(){
</span><span>echo</span> '2016新款女装'<span>;
}
</span><span>function</span><span> showCategory(){
</span><span>echo</span> '女装'<span>;
}
}
</span>?>MaleUserStrategy.php
<?<span>php
namespace Baobab;
</span><span>class</span> MaleUserStrategy <span>implements</span><span> UserStrategy{
</span><span>function</span><span> showAd(){
</span><span>echo</span> 'Iphone6s plus'<span>;
}
</span><span>function</span><span> showCategory(){
</span><span>echo</span> '电子产品'<span>;
}
}
</span>?>index.php
<span>class</span><span> Page{
</span><span>protected</span> <span>$strategy</span><span>;
</span><span>function</span><span> Index(){
</span><span>$this</span>->strategy-><span>showAd();
</span><span>echo</span> '<br/>'<span>;
</span><span>$this</span>->strategy-><span>showCategory();
}
</span><span>function</span> setStrategy(Baobab\UserStrategy <span>$strategy</span><span>){
</span><span>$this</span>->strategy = <span>$strategy</span><span>;
}
}
</span><span>$page</span> = <span>new</span><span> Page();
</span><span>if</span> (<span>isset</span>(<span>$_GET</span>['female'<span>])){
</span><span>$strategy</span> = <span>new</span><span> Baobab\FemaleUserStrategy();
}</span><span>else</span><span>{
</span><span>$strategy</span> = <span>new</span><span> Baobab\MaleUserStrategy();
}
</span><span>$page</span>->setStrategy(<span>$strategy</span><span>);
</span><span>$page</span>->Index();使用策略模式可实现Ioc，依赖倒置、控制反转
