eval（）和spl_autoload_register / __autoload（）只能在运行时创建类吗？

Question

I'm writing a devel module (so please no "you shouldn't do it" comments).

My framework already uses __autoload(), so I cannot use it. I would like to refrain from using eval() and writing temporary files, too. Is there any way to creaet child classes on the fly?

Like, I can create methods using __call() and properties using __get() / __set(), but I would really prefer to dynamically create a subclass. Like, TableUsers as a subclass of Table when working with 'users' table, to make sure properties in class match fields in table.

Answer 1

For this implementation I will start out with a targeted usage:

 include "table.creator:///user_table/TableUsers/id";
 $ut = new TableUsers();

NOTE This should NEVER be used for production code but it is useful for prototyping.

First off define a stream wrapper:

class TableMaker_StreamWrapper {

    protected $_pos = 0;
    protected $_data;
    protected $_stat;

    /**
     * Opens the script file and converts markup.
     */
    public function stream_open($path, $mode, $options, &$opened_path)
    {
        // break path into table name, class name and primary key
        $parts = parse_url($path);
        $dir = $parts["path"];
        list($garbage, $tableName, $className, $primaryKey) = explode("/", $dir, 4);


        $this->_data = '<?php class '.$className.' extends MyBaseClass {'.
        '  protected $primaryKey = "'.$primaryKey.'";'.
        '}';
        return true;
    }


    public function url_stat()
    {
        return $this->_stat;
    }

    public function stream_read($count)
    {
        $ret = substr($this->_data, $this->_pos, $count);
        $this->_pos += strlen($ret);
        return $ret;
    }


    public function stream_tell()
    {
        return $this->_pos;
    }


    public function stream_eof()
    {
        return $this->_pos >= strlen($this->_data);
    }


    public function stream_stat()
    {
        return $this->_stat;
    }


    public function stream_seek($offset, $whence)
    {
        switch ($whence) {
            case SEEK_SET:
                if ($offset < strlen($this->_data) && $offset >= 0) {
                $this->_pos = $offset;
                    return true;
                } else {
                    return false;
                }
                break;

            case SEEK_CUR:
                if ($offset >= 0) {
                    $this->_pos += $offset;
                    return true;
                } else {
                    return false;
                }
                break;

            case SEEK_END:
                if (strlen($this->_data) + $offset >= 0) {
                    $this->_pos = strlen($this->_data) + $offset;
                    return true;
                } else {
                    return false;
                }
                break;

            default:
                return false;
        }
    }
}

Then within our code we have to register the stream wrapper like so.

stream_register_wrapper("table.creator", "TableMaker_StreamWrapper");

Then when you want to create a table wrapper around a class you have but to ...

include("table.creator:///my_table/MyTableClass/id");

and then you will be able to make new MyTableClass to your hearts content.

if you want additional syntactic sugar you can create a little factory function like this.

function get_table($tableName, $className, $pk= "id"){
     if (!class_exists($className)){
          require("table.creator":///".$tableName."/".$className."/".$pk);
     }
     return new $className();
} 

Then you can just say.

$table = get_table("users", "UserTable");

Hope this helps