php声明一个人类，成员属性有姓名、年龄、性别、身高等，成员方法有说话、走路等。声明第一个子类司机类继承人类，成员属性有驾龄，成员方法有开车；声明第二个子类医生类继承人类，成员属性有所在医院、专业，成员方法有治病。还可以自行设计其他子类。

好的，以下是 PHP 代码实现：

class Person {
    protected $name;
    protected $age;
    protected $gender;
    protected $height;
    
    public function __construct($name, $age, $gender, $height) {
        $this->name = $name;
        $this->age = $age;
        $this->gender = $gender;
        $this->height = $height;
    }
    
    public function say() {
        echo "Hello, my name is " . $this->name . ".\n";
    }
    
    public function walk() {
        echo $this->name . " is walking.\n";
    }
}

class Driver extends Person {
    protected $drivingYears;
    
    public function __construct($name, $age, $gender, $height, $drivingYears) {
        parent::__construct($name, $age, $gender, $height);
        $this->drivingYears = $drivingYears;
    }
    
    public function drive() {
        echo $this->name . " is driving for " . $this->drivingYears . " years.\n";
    }
}

class Doctor extends Person {
    protected $hospital;
    protected $specialty;
    
    public function __construct($name, $age, $gender, $height, $hospital, $specialty) {
        parent::__construct($name, $age, $gender, $height);
        $this->hospital = $hospital;
        $this->specialty = $specialty;
    }
    
    public function cure() {
        echo $this->name . " is curing patients in " . $this->hospital . ".\n";
    }
}

// 测试代码
$person = new Person("Tom", 25, "male", 180);
$person->say();
$person->walk();

$driver = new Driver("Mike", 30, "male", 175, 10);
$driver->say();
$driver->walk();
$driver->drive();

$doctor = new Doctor("Lily", 35, "female", 165, "ABC Hospital", "Cardiology");
$doctor->say();
$doctor->walk();
$doctor->cure();

以上代码中，`Person` 类是一个基类，定义了人的基本属性和行为，`Driver` 类继承自 `Person` 类，新增了驾龄属性和开车行为，`Doctor` 类同样继承自 `Person` 类，新增了所在医院和专业属性，以及治病行为。通过多态的方式，我们可以根据需要实例化不同的对象，来调用不同的方法。