反射是指在PHP运行状态中，扩展分析PHP程序，导出或提取出关于类、方法、属性、参数等的详细信息，包括注释。这种动态获取的信息以及动态调用对象的方法的功能称为反射API。反射是操纵面向对象范型中元模型的API，其功能十分强大，可帮助我们构建复杂，可扩展的应用。
php反射api由若干类组成，可帮助我们用来访问程序的元数据或者同相关的注释交互。借助反射我们可以获取诸如类实现了那些方法，创建一个类的实例（不同于用new创建），调用一个方法（也不同于常规调用），传递参数，动态调用类的静态方法。
<?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.";"; }} 
