Use reflection to generate the SQL CREATE statement _ PHP Tutorial

Use reflection to generate the SQL CREATE statement. The following program uses Reflection to construct the CREATETABLE SQL statement. If you are not very familiar with the reflection mechanism, you can look at the charm and role of reflection in this program .? The program under php *** Crea uses Reflection to construct the SQL statement of "CREATE TABLE. If you are not very familiar with the reflection mechanism, you can look at the charm and role of reflection from this program.

  * @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.";";    }}

Explain "create table" SQL statement. If you are not very familiar with the reflection mechanism, you can look at the charm and role of reflection from this program. ? Php/*** Crea...