PHP操作Trait类

用法：通过在类中使用use 关键字，声明要组合的Trait名称，具体的Trait的声明使用Trait关键词，Trait不能实例化

如下代码实例:

trait Dog{
    public $name="dog";
    public function bark(){
        echo "This is dog";
    }
}
class Animal{
    public function eat(){
        echo "This is animal eat";
    }
}
class Cat extends Animal{
    use Dog;
    public function drive(){
        echo "This is cat drive";
    }
}
$cat = new Cat();
$cat->drive();//This is cat drive
echo "<br/>";
$cat->eat();//This is animal eat
echo "<br/>";
$cat->bark();//This is dog

再测试Trait、基类和本类对同名属性或方法的处理，如下代码

trait Dog{
    public $name="dog";
    public function drive(){
        echo "This is dog drive";
    }
    public function eat(){
        echo "This is dog eat";
    }
}

class Animal{
    public function drive(){
        echo "This is animal drive";
    }
    public function eat(){
        echo "This is animal eat";
    }
}

class Cat extends Animal{
    use Dog;
    public function drive(){
        echo "This is cat drive";
    }
}
$cat = new Cat();
$cat->drive();//This is cat drive
echo "<br/>";
$cat->eat();//This is dog eat
```php
所以：Trait中的方法或属性会覆盖 基类中的同名的方法或属性，而本类会覆盖Trait中同名的属性或方法
一个类可以组合多个Trait，通过逗号相隔，如下
use trait1,trait2
当不同的trait中，却有着同名的方法或属性，会产生冲突，可以使用insteadof或 as进行解决，insteadof 是进行替代，而as是给它取别名
如下实例：
```php
trait trait1{
    public function eat(){
        echo "This is trait1 eat";
    }
    public function drive(){
        echo "This is trait1 drive";
    }
}
trait trait2{
    public function eat(){
        echo "This is trait2 eat";
    }
    public function drive(){
        echo "This is trait2 drive";
    }
}
class cat{
    use trait1,trait2{
        trait1::eat insteadof trait2;
        trait1::drive insteadof trait2;
    }
}
class dog{
    use trait1,trait2{
        trait1::eat insteadof trait2;
        trait1::drive insteadof trait2;
        trait2::eat as eaten;
        trait2::drive as driven;
    }
}
$cat = new cat();
$cat->eat();//This is trait1 eat
echo "<br/>";
$cat->drive();//This is trait1 drive
echo "<br/>";
echo "<br/>";
echo "<br/>";
$dog = new dog();
$dog->eat();//This is trait1 eat
echo "<br/>";
$dog->drive();//This is trait1 drive
echo "<br/>";
$dog->eaten();//This is trait2 eat
echo "<br/>";
$dog->driven();//This is trait2 drive

Trait也可以互相组合，还可以使用抽象方法，静态属性，静态方法等，实例如下
trait Cat{
    public function eat(){
        echo "This is Cat eat";
    }
}

trait Dog{
    use Cat;
    public function drive(){
        echo "This is Dog drive";
    }
    abstract public function getName();
    
    public function test(){
        static $num=0;
        $num++;
        echo $num;
    }
    
    public static function say(){
        echo "This is Dog say";
    }
}
class animal{
    use Dog;
    public function getName(){
        echo "This is animal name";
    }
}

$animal = new animal();
$animal->getName();//This is animal name
echo "<br/>";
$animal->eat();//This is Cat eat
echo "<br/>";
$animal->drive();//This is Dog drive
echo "<br/>";
$animal::say();//This is Dog say
echo "<br/>";
$animal->test();//1
echo "<br/>";
$animal->test();//2