A little Object Relational Mapper in PHP

gistfile1.php

<?php

/**
 * A little Object Relational Mapper in PHP
 * @author dennis.hotson@gmail.com
 */

class Post
{
	public $title;
	public $content;
}

class Comment
{
	public $post_id;
	public $name;
	public $content;
}

$db = new Db('blog.db', array('Post', 'Comment'));

$p1 = new Post();
$p1->title = 'Welcome to my Blog!';
$p1->content = 'This is my first post.. cool';
$db->save($p1);

$p2 = new Post();
$p2->title = 'My 2nd post';
$p2->content = '2nd post.. Rad!';
$db->save($p2);

$comment = new Comment();
$comment->post = $p2;
$comment->name = 'Franklin';
$comment->content = 'Cool blog dude...';
$db->save($comment);

$p1->title = 'Welcome to my blaargh!';
$db->save($p1);

$posts = $db->table('Post')->all();
foreach ($posts as $post)
	echo "Post #$post->id : $post->title > $post->content\n";

// ----------

class Db
{
	const primary_key = 'INTEGER PRIMARY KEY';
	const integer = 'INTEGER';
	const string = 'STRING';

	private $_db;

	/**
	 * @param $file The sqlite database file to load
	 * @param $classes The classes to create tables for
	 */
	public function __construct($file, $classes = array())
	{
		$this->_db = new SQLiteDatabase($file);

		foreach ($classes as $class)
			$this->_createTable($class);
	}

	public function table($class)
	{
		return new Finder($this->_db, $class);
	}

	public function save($obj)
	{
		$class = get_class($obj);

		$values = array();
		foreach (get_class_vars($class) as $field => $_)
		{
			if (preg_match('#(.*)_id$#', $field, $matches))
			{
				$f = $matches[1];
				if (isset($obj->$f) && isset($obj->$f->id))
					$obj->$field = $obj->$f->id;
			}

			$values[$field] = $obj->$field;
		}

		if (!isset($obj->id)) // insert
		{
			foreach ($values as $field => $v)
				$values[$field] = "'".sqlite_escape_string($v)."'";

			$sql = sprintf("INSERT INTO %s (%s) VALUES (%s)",
				$class,
				implode(array_keys($values), ', '),
				implode($values, ", ")
			);

			$this->_db->queryExec($sql);
			$obj->id = $this->_db->lastInsertRowid();
		}
		else // update
		{
			foreach ($values as $field => $v)
				$values[$field] = sprintf(
					"%s = '%s'",
					$field,
					sqlite_escape_string($obj->$field)
				);

			$sql = sprintf('UPDATE %s SET %s WHERE id = %d',
				$class,
				implode($values, ', '),
				$obj->id
			);
			$this->_db->queryExec($sql);
		}
	}

	private function _createTable($class)
	{
		$fields = array(
			'id' => array('type' => self::primary_key),
		);

		foreach (get_class_vars($class) as $name => $default)
		{
			if (preg_match('#_id$#', $name)) // foreign keys end in '_id'
				$type = self::integer;
			elseif(is_integer($default))
				$type = self::integer;
			else
				$type = self::string;

			$fields[$name] = array(
				'type' => $type,
				'default' => $default
			);
		}

		$columndefs = array();
		foreach ($fields as $name => $field)
		{
			$columndefs []= sprintf('%s %s%s',
				$name,
				$field['type'],
				isset($field['default'])
					? " DEFAULT '".sqlite_escape_string($field['default'])."'"
					: ''
			);
		}

		$this->_db->queryExec(sprintf('DROP TABLE %s', $class));
		$this->_db->queryExec(sprintf('CREATE TABLE %s (%s)',
			$class,
			implode($columndefs, ', ')
		));
	}
}

class Finder
{
	private $_db;
	private $_class;

	public function __construct($db, $class)
	{
		$this->_db = $db;
		$this->_class = $class;
	}

	public function all()
	{
		$set = $this->_db->arrayQuery(
			sprintf('SELECT * FROM %s', $this->_class),
			SQLITE_ASSOC);

		$result = array();
		foreach ($set as $record)
			$result []= $this->_newModel($record);

		return $result;
	}

	public function findById($id)
	{
		$set = $this->_db->arrayQuery(
			sprintf('SELECT * FROM %s WHERE id = %d', $this->_class, $id),
			SQLITE_ASSOC);

		return count($set) > 0
			? $this->_newModel($set[0])
			: null;
	}

	private function _newModel($record)
	{
		$obj = new $this->_class;
		foreach ($record as $field => $value)
			$obj->$field = $value;
		return $obj;
	}
}