下面的程序使用R纽约娱乐城eflection来构造"CREATE TABLE"的sql语句。如果你不是很熟悉反射机制，可以从这个程序中看看反射的魅力与作用。

<?php/** * Creates an SQL ‘Create Table‘ based upon an entity * * @author Chris Tankersley <chris@ctankersley.com> * @copyright 2010 Chris Tankersley * @package PhpORM_Cli */class PhpORM_Cli_GenerateSql{    /**     * Use a MySQL database     */    const MYSQL = ‘mysql‘;    /**     * Use a SQLite database     */    const SQLITE = ‘sqlite‘;    /**     * Types that are allowed to have a length     * @var array     */    protected $_hasLength = array(‘integer‘, ‘varchar‘);    /**     * Regexes needed to pull out the different comments     * @var array     */    protected $_regexes = array(        ‘type‘ => ‘/ type=([a-z_]*) /‘,        ‘length‘ => ‘/ length=([0-9]*) /‘,        ‘default‘ => ‘/ default="(.*)" /‘,        ‘null‘ => ‘/ null /‘,    );    /**     * Types that we support     * @var array     */    protected $_validTypes = array(        ‘boolean‘ => ‘BOOL‘,        ‘date‘ => ‘DATE‘,        ‘integer‘ => ‘INT‘,        ‘primary_autoincrement‘ => ‘INT AUTO_INCREMENT PRIMARY KEY‘,        ‘text‘ => ‘TEXT‘,        ‘timestamp‘ => ‘TIMESTAMP‘,        ‘varchar‘ => ‘VARCHAR‘,    );    /**     * Name of the class we will interperet     * @var string     */    protected $_className;    /**     * Name of the table we are generating     * @var string     */    protected $_tableName;    /**     * The type of database we are generating     * @var string     */    protected $_type;    /**     * Sets the name of the class we are working with     * @param string $class     * @param string $table_name     * @param string $type     */    public function __construct($class, $table_name, $type = self::MYSQL)    {        $this->_className = $class;        $this->_tableName = $table_name;        $this->_type = $type;    }    /**     * Builds an SQL Line for a property     * @param ReflectionProperty $property     * @return string     */    protected function _getDefinition($property)    {        $type = ‘‘;        $length = ‘‘;        $null = ‘‘;                preg_match($this->_regexes[‘type‘], $property->getDocComment(), $matches);        if(count($matches) == 2) {            if(array_key_exists($matches[1], $this->_validTypes)) {                $type = $this->_validTypes[$matches[1]];                if(in_array($matches[1], $this->_hasLength)) {                    $length = $this->_getLength($property);                }                if($matches[1] != ‘primary_autoincrement‘) {                    $null = $this->_getNull($property);                }                $sql = ‘`‘.$property->getName().‘` ‘.$type.‘ ‘.$length.‘ ‘.$null;                return $sql;            } else {                throw new Exception(‘Type "‘.$matches[1].‘" is not a supported SQL type‘);            }        } else {            throw new Exception(‘Found ‘.count($matches).‘ when checking Type for property ‘.$property->getName());        }    }    /**     * Extracts the Length from a property     * @param ReflectionProperty $property     * @return string     */    protected function _getLength($property)    {        preg_match($this->_regexes[‘length‘], $property->getDocComment(), $matches);        if(count($matches) == 2) {            return ‘(‘.$matches[1].‘)‘;        } else {            return ‘‘;        }    }    /**     * Determines if a Property is allowed to be null     * @param ReflectionProperty $property     * @return string     */    protected function _getNull($property)    {        preg_match($this->_regexes[‘null‘], $property->getDocComment(), $matches);        if(count($matches) == 1) {            return ‘NULL‘;        } else {            return ‘NOT NULL‘;        }    }    /**     * Generates a block of SQL to create a table from an Entity     * @return string     */    public function getSql()    {        $class = new ReflectionClass($this->_className);        $definitions = array();        foreach($class->getProperties() as $property) {            if(strpos($property->getName(), ‘_‘) === false) {                $definitions[] = $this->_getDefinition($property);            }        }        $columns = implode(",n", $definitions);                $sql = "CREATE TABLE ".$this->_tableName." (".$columns.")";        if($this->_type == self::MYSQL) {            $sql .= " ENGINE=MYISAM";        }        return $sql.";";    }}

用反射来生成SQL的CREATE语句