使用PHP反射机制来构造"CREATE TABLE"的sql语句

<?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.";";
  }
}