PDO based port of PEAR's DB_DataObject

Model.php

<?php
namespace Framework;
use \PDO;
use \Exception;
abstract class Model {
    
    private static $_host;
    private static $_username;
    private static $_password;
    private static $_database;
    private static $_pdo;
    private static $_schema = array();
    
    private $_stmt;
    private $_select;
    private $_join = array();
    private $_where = array();
    private $_group_by;

    public function __construct() {

        $this->_select = array($this->getTable() . '.*');
    }

    public static function configure($host, $username, $password, $database) {

        self::$_host = $host;
        self::$_username = $username;
        self::$_password = $password;
        self::$_database = $database;
        
        // Load the schmea file
        $config = CONFIG_DIR . '/' . basename(self::$_database) . '.schema.php';
        if (!is_file($config)) {
            throw new \Exception("Failed to load schema file: $config"); 
        } else {
            require_once $config;
        }

    }

    private function getDSN() {
        
        return 'mysql:host=' .  self::$_host . ';dbname=' . self::$_database;
    }

    protected function getPDO() {
        
        if (empty(self::$_pdo)) {
            self::$_pdo = new PDO($this->getDSN(), self::$_username, self::$_password);
            //self::$_pdo->beginTransaction();
        }

        return self::$_pdo;
    }
    
    public function getTable() {
        $path = explode('\\', get_class($this));
        return strtolower(end($path));
    }
    
    public function find($params = array()) {

        $this->_stmt = $this->getPDO()->prepare($this->buildSelect());

        foreach($this->getColumnMap() as $key => $value) {
            $params[":$key"] = $value; 
        }

        $res = $this->_stmt->execute($params);
        return $this->_stmt->rowCount();
    }

    public function fetch() {
        
        $row = $this->_stmt->fetch(PDO::FETCH_ASSOC);
        if ($row !== false) {
            $this->setFrom($row); 
        }
        
        return $row;
        //return $row === false ? false : true;
    }

    public function setFrom(array $source) {
        $cols = self::$_schema[$this->getTable()];
        foreach($source as $key => $value) {
           if (isset($cols[$key])) {
                $this->$key = $value;
           }
        }
    }
    
    public function selectAdd($clause = null) {
        
        if ($clause === null) {
            $this->_select = array();
        } else {
            $this->_select[] = $clause;
        }
    }
    
    public function joinAdd($join) {
        $this->_join[] = $join;
    }
    public function whereAdd($clause, $conjunction = 'AND') {
        $this->_where[] = array($clause, $conjunction);
    }

    public function groupBy($group_by) {
        $this->_group_by = $group_by;
    }

    public function get($a, $b = null) {

        $col = empty($b) ? 'id' : $a;
        $val = empty($b) ? $a : $b;

        $table = $this->getTable();
        $this->_stmt = $this->getPDO()->prepare("SELECT * from $table WHERE $col = :$col");
        $this->_stmt->bindParam(":$col", $val, PDO::PARAM_INT);
        $this->_stmt->execute();

        return $this->fetch();
    }

    public function delete() {
        
        $table = $this->getTable();
        $this->_stmt = $this->getPDO()->prepare("DELETE FROM $table WHERE id = :id");
        $this->_stmt->bindParam('id', $this->id, PDO::PARAM_INT);
        return $this->_stmt->execute();
    }

    public function insert() {
        
        $map = $this->getColumnMap();
        if (isset($map['id'])) {
            unset($map['id']);
        }

        $cols = array_keys($map);
        $vals = array_values($map);
        $params = array_map(function($value) { return ":$value"; }, $cols);
        $table = $this->getTable();

        $sql = "INSERT INTO $table (" . join(',', $cols) . ') VALUES (' . join(',', $params) . ')';

        $this->_stmt = $this->getPDO()->prepare($sql);
        for ($i = 0; $i < count($params); $i++) {
            $this->_stmt->bindValue($params[$i], $vals[$i]);
        }
            
        $result = $this->_stmt->execute();
        if ($result) {
            $this->id = $this->getPDO()->lastInsertId();
        }

        return $result;
    }

    public function update() {
        
        $map = $this->getColumnMap();
        $values = array();
        $sql = 'UPDATE ' . $this->getTable() . ' SET ';
        foreach($this->getColumnMap() as $col => $value) {
            if ($col == 'id') { continue; }
            $sep = empty($values) ? '' : ',';
            $sql .= "$sep $col = :$col";
            $values[":$col"] = $value;
        }
        $sql .= " WHERE ID = :id";
        $values[':id'] = $this->id;
            
        $this->_stmt = $this->getPDO()->prepare($sql);
        $result = $this->_stmt->execute($values);
        return $result;
    }
    
    public function buildSelect() {
        
        $table = $this->getTable();

        $sql = 'SELECT ' . implode(',', $this->_select);
        $sql .= ' FROM ' . $this->getTable();
        
        foreach($this->_join as $join) {
            $sql .= " $join";
        }

        /**
         * Build where where clauses.
         */
        $where = array();
        $map = $this->getColumnMap();
        foreach($map as $col => $value) {
            $where[] = array("$col = :$col", 'AND'); 
        }
        $where = array_merge($this->_where, $where);
        
        if (!empty($where)) {
            $sql .= ' WHERE';
            for($i = 0; $i < count($where); $i++) {
                list($clause, $conjunction) = $where[$i];
                $sql .= $i == 0 ? " $clause" : " $conjunction $clause";
            }
        }

        

        if (!empty($this->_group_by)) {
            $sql .= " GROUP BY {$this->_group_by}";
        }

        return $sql;
    }


    public function commit() {
        $this->getPDO()->commit();
    }

    public function lastError() {
        return $this->_stmt->errorInfo();
    }

    private function getColumnMap() {
        $map = array();
        $cols = self::$_schema[$this->getTable()];
        foreach($cols as $col => $v) {
            if (isset($this->$col)) {
                $map[$col] = $this->$col; 
            }
        }
        return $map;
    }

    public function __clone() {

        if (!empty($this->_stmt)) {
            $this->_stmt = null;
        }
    }
}

Ditto