性状 Trait
性状(Trait)是PHP5.4.0引入的概念，既像接口，也像类，但是两者都不是。
性状有两个作用：1.表明类可以做什么（像接口）；2.将代码模块化（像类)。
性状能把模块化的实现方式注入多个无关的类中（类与类之间没有业务功能相似处），而且还能促进代码重构。
性状创建：
trait MyTrait
{
protected $trait_test_var;
protected $trait_test_result;
public function setVar($test_var)
{
$this->trait_test_var = $test_var;
$this->trait_test_result = $this->trait_test_var + 1;
}
public function getVarResult()
{
return $this->trait_test_result;
}
}
然后，再创建一个测试类：
// 父类（交通工具）
class Vehicle
{
protected $driver;
protected $drive_style;
public function __construct($driver)
{
$this->driver = $driver;
}
public function doThing()
{
echo ‘I am ‘ . $driver . ‘ and,i am driving‘;
}
}
//子类(小汽车)
class Car extends Vehicle
{
public function doThing()
{
echo ‘I am ‘ . $this->driver . ‘ and,i am driving car‘;
}
}
创建好之后。
在子类car中加入"use MyTrait"
class Car extends Vehicle
{
use MyTrait;
public function doThing()
{
echo ‘I am ‘ . $this->driver . ‘ and,i am driving car‘;
}
}
然后，使用car：
$car = new Car(‘jeep‘);
$car->setVar(1);
var_dump($car->getVarResult()); // 输出 2
如果还有另外一辆车，例如 jeep
class Jeep extends Vehicle
{
public function doThing()
{
echo ‘I am ‘ . $this->driver . ‘ and i am driving jeep‘;
}
}
这辆 jeep也想使用 MyTrait 时，我们也可以在其中加入 "use MyTrait"，像这样
class Jeep extends Vehicle
{
use MyTrait;
public function doThing()
{
echo ‘I am ‘ . $this->driver . ‘ and i am driving jeep‘;
}
}
然后使用：
$car = new Car(‘jeep‘);
$car->setVar(1);
var_dump($car->getVarResult()); // 输出 2
$jeep = new Jeep(‘jeep‘);
$jeep->setVar(3);
var_dump($jeep->getVarResult()); // 输出 4
但是，这样每一个子类中都使用"use MyTrait "引入，这样做不大好，可以进行优化。
可以在父类Vehicle中使用"use MyTrait"引入，像这样：
class Vehicle
{
use MyTrait;
protected $driver;
protected $drive_style;
public function __construct($driver)
{
$this->driver = $driver;
}
public function doThing()
{
echo ‘I am ‘ . $driver . ‘ and,i am driving‘;
}
}
class Car extends Vehicle
{
#use MyTrait;
public function doThing()
{
echo ‘I am ‘ . $this->driver . ‘ and,i am driving car‘;
}
}
class Jeep extends Vehicle
{
#use MyTrait;
public function doThing()
{
echo ‘I am ‘ . $this->driver . ‘ and i am driving jeep‘;
}
}
这样做，同样可以使用。
完整代码如下：
trait MyTrait
{
protected $trait_test_var;
protected $trait_test_result;
public function setVar($test_var)
{
$this->trait_test_var = $test_var;
$this->trait_test_result = $this->trait_test_var + 1;
}
public function getVarResult()
{
return $this->trait_test_result;
}
}
class Vehicle
{
use MyTrait;
protected $driver;
protected $drive_style;
public function __construct($driver)
{
$this->driver = $driver;
}
public function doThing()
{
echo ‘I am ‘ . $driver . ‘ and,i am driving‘;
}
}
class Car extends Vehicle
{
#use MyTrait;
public function doThing()
{
echo ‘I am ‘ . $this->driver . ‘ and,i am driving car‘;
}
}
class Jeep extends Vehicle
{
#use MyTrait;
public function doThing()
{
echo ‘I am ‘ . $this->driver . ‘ and i am driving jeep‘;
}
}
$car = new Car(‘jeep‘);
$car->setVar(1);
var_dump($car->getVarResult()); // 输出 2
$jeep = new Jeep(‘jeep‘);
$jeep->setVar(3);
var_dump($jeep->getVarResult());
原文：https://www.cnblogs.com/benbenhan/p/12450226.html