php5 download implements the code of a PHP5 getter/setter base class

Both PHP3 and PHP4 have classes, but their class definitions are really not decent, and their efficiency is quite embarrassing. However, the information says that PHP5 has restructured object-oriented support. Although it is not completely object-oriented, it can be used. Meet someone.
I started this thing last night when I was bored. I feel that the class member permission keyword added in PHP5 is very good, but the problem comes again. It seems that there is no convenient way to define the getter and setter of the field. The traditional way is Defined like this:
class a
{
private $field;
public function get_field() { return $this->$field; }
public function set_field($value) { $this->field = $value; }
}
Although it is very easy to implement, to be honest, it is really uncomfortable to write this bunch of code for a field. .
So I thought about whether there was a more convenient way to solve it and easily define its type restrictions or something.
I’ve been tinkering with it for a long time (I can’t help it, I’m not familiar with it.)），终于弄出一个类来解决这个问题：
class abstract_entity
{
    private $fields;
    private $sys_type = array(
        "bool" => "",
        "array" => "",
        "double" => "",
        "float" => "",
        "int" => "",
        "integer" => "",
        "long " => "",
        "null" => "",
        "object" => "",
        "real" => "",
        "resource" => "",
        "string" => ""
        // "mixed" and "number"
        );
    protected function __construct($fields)
    {
        /*********************************
         * $fields = array(
         *     "id" = array(
         *        "allow_null" = false,
         *        "value" = 1,
         *        "type" = "int"
         *     );
         * );
        **********************************/
        $this->fields = $fields;
    }
    public function __get($key)
    {
        if(array_key_exists($key, $this->fields))
        {
            return $this->fields[$key]["value"];
        }
        else
        {
            throw new Exception("该属性不存在");
        }
    }
    public function __set($key, $value)
    {
        if(array_key_exists($key, $this->fields))
        {
            $allow_null = $this->fields[$key]["allow_null"];
            $type = $this->fields[$key]["type"];
            if(array_key_exists($type, $this->sys_type))
            {
                $fun = create_function('$value', "return is_$type($value);");
                if(@$fun($value))
                {
                    $this->fields[$key]["value"] = $value;
                }
                else if($allow_null && is_null($value))
                {
                    $this->fields[$key]["value"] = NULL;
                }
                else
                {
                    throw new Exception("该值类型不正确，必须为" . $type . "类型");
                }
            }
            else if($type == "mixed")
            {
                if(!is_null($value))
                {
                    $this->fields[$key]["value"] = $value;
                }
                else if($allow_null)
                {
                    $this->fields[$key]["value"] = NULL;
                }
                else
                {
                    throw new Exception("该值不允许为NULL值");
                }
            }
            else if($type == "number")
            {
                if(is_int($value) || is_float($value))
                {
                    $this->fields[$key]["value"] = $value;
                }
                else if(is_null($value) && $allow_null)
                {
                    $this->fields[$key]["value"] = NULL;
                }
                else
                {
                    throw new Exception("该值类型不正确，必须为" . $type . "类型");
                }
            }
            else
            {
                if(class_exists($type) || interface_exists($type))
                {
                    if(is_subclass_of($value, $type))
                    {
                        $this->fields[$key]["value"] = $value;
                    }
                    else if(is_null($value) && $allow_null)
                    {
                        $this->fields[$key]["value"] = NULL;
                    }
                    else
                    {
                        throw new Exception("该值类型不正确，必须为" . $type . "类型");
                    }
                }
                else if(is_null($value) && $allow_null)
                {
                    $this->fields[$key]["value"] = NULL;
                }
            }
        }
        else
        {
            throw new Exception("该属性不存在");
        }
    }
}
通过定义一个一定格式的array可以比较方便地定义该字段的类型、是否允许NULL值以及默认值。
测试代码如下：
class test extends abstract_entity
{
    public function __construct()
    {
         $define = array(
            "id" => array(
                "allow_null" => false,
                "value" => 1,
                "type" => "int"
            ),
            "name" => array(
                "allow_null" => false,
                "value" => "abc",
                "type" => "string"
            ),
            "gender" => array(
                "allow_null" => false,
                "value" => true,
                "type" => "bool"
            ),
            "ins" => array(
                "allow_null" => false,
                "value" => $this,
                "type" => "test"
                ),
            "ins1" => array(
                "allow_null" => true,
                "value" => $this,
                "type" => "test"
                ),
            "ins2" => array(
                "allow_null" => true,
                "value" => NULL,
                "type" => "config_media_type"
                )
        );
        parent::__construct($define);
    }
}
$a = new test();
$a->id = 123;
eche $a->id;
echo $a->ins1;
$a->ins1 = NULL;
echo is_null($a->ins1);
这里边实现了getter以及setter，但由于时间关系我没去实现readonly的功能，其实很简单，就是再加一项，标识它能不能被改写就成

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