Quentin Zervaas's DBO-PHP Tutorial-php.cn

Quentin Zervaas, the author of "Web 2.0 Development in Practice", mentioned a simple PHP data access object in the book.

/**
* DatabaseObject
*
* Abstract class used to easily manipulate data in a database table
* via simple load/save/delete methods
*/
abstract class DatabaseObject
{
const TYPE_TIMESTAMP = 1;
const TYPE_BOOLEAN = 2;
protected static $types = array(self::TYPE_TIMESTAMP, self::TYPE_BOOLEAN);
private $_id = null;
private $_properties = array();
protected $_db = null;
protected $_table = '';
protected $_idField = '';
public function __construct(Zend_Db_Adapter_Abstract $db, $table, $idField)
{
$this->_db = $db;
$this->_table = $table;
$this->_idField = $idField;
}
public function load($id, $field = null)
{
if (strlen($field) == 0)
$field = $this->_idField;
if ($field == $this->_idField) {
$id = (int) $id;
if ($id <= 0)
return false;
}
$query = sprintf('select %s from %s where %s = ?',
join(', ', $this->getSelectFields()),
$this->_table,
$field);
$query = $this->_db->quoteInto($query, $id);
return $this->_load($query);
}
protected function getSelectFields($prefix = '')
{
$fields = array($prefix . $this->_idField);
foreach ($this->_properties as $k => $v)
$fields[] = $prefix . $k;
return $fields;
}
protected function _load($query)
{
$result = $this->_db->query($query);
$row = $result->fetch();
if (!$row)
return false;
$this->_init($row);
$this->postLoad();
return true;
}
public function _init($row)
{
foreach ($this->_properties as $k => $v) {
$val = $row[$k];
switch ($v['type']) {
case self::TYPE_TIMESTAMP:
if (!is_null($val))
$val = strtotime($val);
break;
case self::TYPE_BOOLEAN:
$val = (bool) $val;
break;
}
$this->_properties[$k]['value'] = $val;
}
$this->_id = (int) $row[$this->_idField];
}
public function save($useTransactions = true)
{
$update = $this->isSaved();
if ($useTransactions)
$this->_db->beginTransaction();
if ($update)
$commit = $this->preUpdate();
else
$commit = $this->preInsert();
if (!$commit) {
if ($useTransactions)
$this->_db->rollback();
return false;
}
$row = array();
foreach ($this->_properties as $k => $v) {
if ($update && !$v['updated'])
continue;
switch ($v['type']) {
case self::TYPE_TIMESTAMP:
if (!is_null($v['value'])) {
if ($this->_db instanceof Zend_Db_Adapter_Pdo_Pgsql)
$v['value'] = date('Y-m-d H:i:sO', $v['value']);
else
$v['value'] = date('Y-m-d H:i:s', $v['value']);
}
break;
case self::TYPE_BOOLEAN:
$v['value'] = (int) ((bool) $v['value']);
break;
}
$row[$k] = $v['value'];
}
if (count($row) > 0) {
// perform insert/update
if ($update) {
$this->_db->update($this->_table, $row, sprintf('%s = %d', $this->_idField, $this->getId()));
}
else {
$this->_db->insert($this->_table, $row);
$this->_id = $this->_db->lastInsertId($this->_table, $this->_idField);
}
}
// update internal id
if ($commit) {
if ($update)
$commit = $this->postUpdate();
else
$commit = $this->postInsert();
}
if ($useTransactions) {
if ($commit)
$this->_db->commit();
else
$this->_db->rollback();
}
return $commit;
}
public function delete($useTransactions = true)
{
if (!$this->isSaved())
return false;
if ($useTransactions)
$this->_db->beginTransaction();
$commit = $this->preDelete();
if ($commit) {
$this->_db->delete($this->_table, sprintf('%s = %d', $this->_idField, $this->getId()));
}
else {
if ($useTransactions)
$this->_db->rollback();
return false;
}
$commit = $this->postDelete();
$this->_id = null;
if ($useTransactions) {
if ($commit)
$this->_db->commit();
else
$this->_db->rollback();
}
return $commit;
}
public function isSaved()
{
return $this->getId() > 0;
}
public function getId()
{
return (int) $this->_id;
}
public function getDb()
{
return $this->_db;
}
public function __set($name, $value)
{
if (array_key_exists($name, $this->_properties)) {
$this->_properties[$name]['value'] = $value;
$this->_properties[$name]['updated'] = true;
return true;
}
return false;
}
public function __get($name)
{
return array_key_exists($name, $this->_properties) ? $this->_properties[$name]['value'] : null;
}
protected function add($field, $default = null, $type = null)
{
$this->_properties[$field] = array('value' => $default,
'type' => in_array($type, self::$types) ? $type : null,
'updated' => false);
}
protected function preInsert()
{
return true;
}
protected function postInsert()
{
return true;
}
protected function preUpdate()
{
return true;
}
protected function postUpdate()
{
return true;
}
protected function preDelete()
{
return true;
}
protected function postDelete()
{
return true;
}
protected function postLoad()
{
return true;
}
public static function BuildMultiple($db, $class, $data)
{
$ret = array();
if (!class_exists($class))
throw new Exception('Undefined class specified: ' . $class);
$testObj = new $class($db);
if (!$testObj instanceof DatabaseObject)
throw new Exception('Class does not extend from DatabaseObject');
foreach ($data as $row) {
$obj = new $class($db);
$obj->_init($row);
$ret[$obj->getId()] = $obj;
}
return $ret;
}
}