MySQLi to PDO

class DBLayer
{
    var $prefix;
    var $link_id;
    var $query_result;

    var $saved_queries = array();
    var $num_queries = 0;

    var $datatype_transformations = array(
        '/^SERIAL$/'    =>  'INT(10) UNSIGNED AUTO_INCREMENT'
    );


    function DBLayer($db_host, $db_username, $db_password, $db_name, $db_prefix, $p_connect)
    {
        $this->prefix = $db_prefix;

        // Was a custom port supplied with $db_host?
        if (strpos($db_host, ':') !== false)
            list($db_host, $db_port) = explode(':', $db_host);

        $p_connect = $p_connect && version_compare(PHP_VERSION, '5.3.0', '>=') ? 'p:' : '';

        if (isset($db_port))
            $this->link_id = @new PDO($p_connect.$db_host, $db_username, $db_password, $db_name, $db_port);
        else
            $this->link_id = @new PDO($p_connect.$db_host, $db_username, $db_password, $db_name);

        if (!$this->link_id)
            error('Unable to connect to MySQL server. MySQL say '.mysqli_connect_error(), __FILE__, __LINE__);

        // Setup the client-server character set (UTF-8)
        if (!defined('FORUM_NO_SET_NAMES'))
            $this->set_names('utf8');

        return $this->link_id;
    }


    function start_transaction()
    {
        return;
    }


    function end_transaction()
    {
        return;
    }


    function query($sql, $unbuffered = false)
    {
        if (strlen($sql) > 140000)
            die('Insanely great request. Interrupted.');

        if (defined('FORUM_SHOW_QUERIES'))
            $q_start = get_microtime();

        $this->query_result = @mysqli_query($this->link_id, $sql);

        if ($this->query_result)
        {
            if (defined('FORUM_SHOW_QUERIES'))
                $this->saved_queries[] = array($sql, sprintf('%.5f', get_microtime() - $q_start));

            ++$this->num_queries;

            return $this->query_result;
        }
        else
        {
            if (defined('FORUM_SHOW_QUERIES'))
                $this->saved_queries[] = array($sql, 0);

            return false;
        }
    }


    function query_build($query, $return_query_string = false, $unbuffered = false)
    {
        $sql = '';

        if (isset($query['SELECT']))
        {
            $sql = 'SELECT '.$query['SELECT'].' FROM '.(isset($query['PARAMS']['NO_PREFIX']) ? '' : $this->prefix).$query['FROM'];

            if (isset($query['JOINS']))
            {
                foreach ($query['JOINS'] as $cur_join)
                    $sql .= ' '.key($cur_join).' '.(isset($query['PARAMS']['NO_PREFIX']) ? '' : $this->prefix).current($cur_join).' ON '.$cur_join['ON'];
            }

            if (!empty($query['WHERE']))
                $sql .= ' WHERE '.$query['WHERE'];
            if (!empty($query['GROUP BY']))
                $sql .= ' GROUP BY '.$query['GROUP BY'];
            if (!empty($query['HAVING']))
                $sql .= ' HAVING '.$query['HAVING'];
            if (!empty($query['ORDER BY']))
                $sql .= ' ORDER BY '.$query['ORDER BY'];
            if (!empty($query['LIMIT']))
                $sql .= ' LIMIT '.$query['LIMIT'];
        }
        else if (isset($query['INSERT']))
        {
            $sql = 'INSERT INTO '.(isset($query['PARAMS']['NO_PREFIX']) ? '' : $this->prefix).$query['INTO'];

            if (!empty($query['INSERT']))
                $sql .= ' ('.$query['INSERT'].')';

            if (is_array($query['VALUES']))
                $sql .= ' VALUES('.implode('),(', $query['VALUES']).')';
            else
                $sql .= ' VALUES('.$query['VALUES'].')';
        }
        else if (isset($query['UPDATE']))
        {
            $query['UPDATE'] = (isset($query['PARAMS']['NO_PREFIX']) ? '' : $this->prefix).$query['UPDATE'];

            $sql = 'UPDATE '.$query['UPDATE'].' SET '.$query['SET'];

            if (!empty($query['WHERE']))
                $sql .= ' WHERE '.$query['WHERE'];
        }
        else if (isset($query['DELETE']))
        {
            $sql = 'DELETE FROM '.(isset($query['PARAMS']['NO_PREFIX']) ? '' : $this->prefix).$query['DELETE'];

            if (!empty($query['WHERE']))
                $sql .= ' WHERE '.$query['WHERE'];
        }
        else if (isset($query['REPLACE']))
        {
            $sql = 'REPLACE INTO '.(isset($query['PARAMS']['NO_PREFIX']) ? '' : $this->prefix).$query['INTO'];

            if (!empty($query['REPLACE']))
                $sql .= ' ('.$query['REPLACE'].')';

            $sql .= ' VALUES('.$query['VALUES'].')';
        }

        return ($return_query_string) ? $sql : $this->query($sql, $unbuffered);
    }


    function result($query_id = 0, $row = 0, $col = 0)
    {
        if ($query_id)
        {
            if ($row)
                @mysqli_data_seek($query_id, $row);

            $cur_row = @mysqli_fetch_row($query_id);
            return $cur_row[$col];
        }
        else
            return false;
    }


    function fetch_assoc($query_id = 0)
    {
        return ($query_id) ? @mysqli_fetch_assoc($query_id) : false;
    }


    function fetch_row($query_id = 0)
    {
        return ($query_id) ? @mysqli_fetch_row($query_id) : false;
    }


    function num_rows($query_id = 0)
    {
        return ($query_id) ? @mysqli_num_rows($query_id) : false;
    }


    function affected_rows()
    {
        return ($this->link_id) ? @mysqli_affected_rows($this->link_id) : false;
    }


    function insert_id()
    {
        return ($this->link_id) ? @mysqli_insert_id($this->link_id) : false;
    }


    function get_num_queries()
    {
        return $this->num_queries;
    }


    function get_saved_queries()
    {
        return $this->saved_queries;
    }


    function free_result($query_id = false)
    {
        return ($query_id) ? @mysqli_free_result($query_id) : false;
    }


    function escape($str)
    {
        return is_array($str) ? '' : mysqli_real_escape_string($this->link_id, $str);
    }


    function error()
    {
        $result['error_sql'] = @current(@end($this->saved_queries));
        $result['error_no'] = @mysqli_errno($this->link_id);
        $result['error_msg'] = @mysqli_error($this->link_id);

        return $result;
    }


    function close()
    {
        if ($this->link_id)
        {
            if ($this->query_result)
                @mysqli_free_result($this->query_result);

            return @mysqli_close($this->link_id);
        }
        else
            return false;
    }


    function set_names($names)
    {
        return $this->query('SET NAMES \''.$this->escape($names).'\'');
    }


    function get_version()
    {
        $result = $this->query('SELECT VERSION()');

        return array(
            'name'      => 'MySQL Improved',
            'version'   => preg_replace('/^([^-]+).*$/', '\\1', $this->result($result))
        );
    }


    function table_exists($table_name, $no_prefix = false)
    {
        $result = $this->query('SHOW TABLES LIKE \''.($no_prefix ? '' : $this->prefix).$this->escape($table_name).'\'');
        return $this->num_rows($result) > 0;
    }


    function field_exists($table_name, $field_name, $no_prefix = false)
    {
        $result = $this->query('SHOW COLUMNS FROM '.($no_prefix ? '' : $this->prefix).$table_name.' LIKE \''.$this->escape($field_name).'\'');
        return $this->num_rows($result) > 0;
    }


    function index_exists($table_name, $index_name, $no_prefix = false)
    {
        $exists = false;

        $result = $this->query('SHOW INDEX FROM '.($no_prefix ? '' : $this->prefix).$table_name);
        while ($cur_index = $this->fetch_assoc($result))
        {
            if ($cur_index['Key_name'] == ($no_prefix ? '' : $this->prefix).$table_name.'_'.$index_name)
            {
                $exists = true;
                break;
            }
        }

        return $exists;
    }


    function create_table($table_name, $schema, $no_prefix = false)
    {
        if ($this->table_exists($table_name, $no_prefix))
            return;

        $query = 'CREATE TABLE '.($no_prefix ? '' : $this->prefix).$table_name." (\n";

        // Go through every schema element and add it to the query
        foreach ($schema['FIELDS'] as $field_name => $field_data)
        {
            $field_data['datatype'] = preg_replace(array_keys($this->datatype_transformations), array_values($this->datatype_transformations), $field_data['datatype']);

            $query .= $field_name.' '.$field_data['datatype'];

            if (isset($field_data['collation']))
                $query .= 'CHARACTER SET utf8 COLLATE utf8_'.$field_data['collation'];

            if (!$field_data['allow_null'])
                $query .= ' NOT NULL';

            if (isset($field_data['default']))
                $query .= ' DEFAULT '.$field_data['default'];

            $query .= ",\n";
        }

        // If we have a primary key, add it
        if (isset($schema['PRIMARY KEY']))
            $query .= 'PRIMARY KEY ('.implode(',', $schema['PRIMARY KEY']).'),'."\n";

        // Add unique keys
        if (isset($schema['UNIQUE KEYS']))
        {
            foreach ($schema['UNIQUE KEYS'] as $key_name => $key_fields)
                $query .= 'UNIQUE KEY '.($no_prefix ? '' : $this->prefix).$table_name.'_'.$key_name.'('.implode(',', $key_fields).'),'."\n";
        }

        // Add indexes
        if (isset($schema['INDEXES']))
        {
            foreach ($schema['INDEXES'] as $index_name => $index_fields)
                $query .= 'KEY '.($no_prefix ? '' : $this->prefix).$table_name.'_'.$index_name.'('.implode(',', $index_fields).'),'."\n";
        }

        // We remove the last two characters (a newline and a comma) and add on the ending
        $query = substr($query, 0, strlen($query) - 2)."\n".') ENGINE='.(isset($schema['ENGINE']) ? $schema['ENGINE'] : 'MyISAM').' CHARACTER SET utf8';

        $this->query($query) or error(__FILE__, __LINE__);
    }


    function drop_table($table_name, $no_prefix = false)
    {
        if (!$this->table_exists($table_name, $no_prefix))
            return;

        $this->query('DROP TABLE '.($no_prefix ? '' : $this->prefix).$table_name) or error(__FILE__, __LINE__);
    }


    function add_field($table_name, $field_name, $field_type, $allow_null, $default_value = null, $after_field = null, $no_prefix = false)
    {
        if ($this->field_exists($table_name, $field_name, $no_prefix))
            return;

        $field_type = preg_replace(array_keys($this->datatype_transformations), array_values($this->datatype_transformations), $field_type);

        if ($default_value !== null && !is_int($default_value) && !is_float($default_value))
            $default_value = '\''.$this->escape($default_value).'\'';

        $this->query('ALTER TABLE '.($no_prefix ? '' : $this->prefix).$table_name.' ADD '.$field_name.' '.$field_type.($allow_null ? ' ' : ' NOT NULL').($default_value !== null ? ' DEFAULT '.$default_value : ' ').($after_field != null ? ' AFTER '.$after_field : '')) or error(__FILE__, __LINE__);
    }


    function alter_field($table_name, $field_name, $field_type, $allow_null, $default_value = null, $after_field = null, $no_prefix = false)
    {
        if (!$this->field_exists($table_name, $field_name, $no_prefix))
            return;

        $field_type = preg_replace(array_keys($this->datatype_transformations), array_values($this->datatype_transformations), $field_type);

        if ($default_value !== null && !is_int($default_value) && !is_float($default_value))
            $default_value = '\''.$this->escape($default_value).'\'';

        $this->query('ALTER TABLE '.($no_prefix ? '' : $this->prefix).$table_name.' MODIFY '.$field_name.' '.$field_type.($allow_null ? ' ' : ' NOT NULL').($default_value !== null ? ' DEFAULT '.$default_value : ' ').($after_field != null ? ' AFTER '.$after_field : '')) or error(__FILE__, __LINE__);
    }


    function rename_field($table_name, $field_name, $field_new_name, $field_type, $allow_null, $default_value = null, $no_prefix = false)
    {
        if (!$this->field_exists($table_name, $field_name, $no_prefix))
            return;

        $field_type = preg_replace(array_keys($this->datatype_transformations), array_values($this->datatype_transformations), $field_type);

        if ($default_value !== null && !is_int($default_value) && !is_float($default_value))
            $default_value = '\''.$this->escape($default_value).'\'';

        $this->query('ALTER TABLE '.($no_prefix ? '' : $this->prefix).$table_name.' CHANGE '.$field_name.' '.$field_new_name.' '.$field_type.($allow_null ? ' ' : ' NOT NULL').($default_value !== null ? ' DEFAULT '.$default_value : ' ')) or error(__FILE__, __LINE__);
    }


    function drop_field($table_name, $field_name, $no_prefix = false)
    {
        if (!$this->field_exists($table_name, $field_name, $no_prefix))
            return;

        $this->query('ALTER TABLE '.($no_prefix ? '' : $this->prefix).$table_name.' DROP '.$field_name) or error(__FILE__, __LINE__);
    }


    function add_index($table_name, $index_name, $index_fields, $unique = false, $no_prefix = false)
    {
        if ($this->index_exists($table_name, $index_name, $no_prefix))
            return;

        $this->query('ALTER TABLE '.($no_prefix ? '' : $this->prefix).$table_name.' ADD '.($unique ? 'UNIQUE ' : '').'INDEX '.($no_prefix ? '' : $this->prefix).$table_name.'_'.$index_name.' ('.implode(',', $index_fields).')') or error(__FILE__, __LINE__);
    }


    function drop_index($table_name, $index_name, $no_prefix = false)
    {
        if (!$this->index_exists($table_name, $index_name, $no_prefix))
            return;

        $this->query('ALTER TABLE '.($no_prefix ? '' : $this->prefix).$table_name.' DROP INDEX '.($no_prefix ? '' : $this->prefix).$table_name.'_'.$index_name) or error(__FILE__, __LINE__);
    }
}