medoo::where_clause PHP Method

    protected function where_clause($where)
    {
        $where_clause = '';
        if (is_array($where)) {
            $where_keys = array_keys($where);
            $where_AND = preg_grep("/^AND\\s*#?\$/i", $where_keys);
            $where_OR = preg_grep("/^OR\\s*#?\$/i", $where_keys);
            $single_condition = array_diff_key($where, array_flip(explode(' ', 'AND OR GROUP ORDER HAVING LIMIT LIKE MATCH')));
            if ($single_condition != array()) {
                $where_clause = ' WHERE ' . $this->data_implode($single_condition, '');
            }
            if (!empty($where_AND)) {
                $value = array_values($where_AND);
                $where_clause = ' WHERE ' . $this->data_implode($where[$value[0]], ' AND');
            }
            if (!empty($where_OR)) {
                $value = array_values($where_OR);
                $where_clause = ' WHERE ' . $this->data_implode($where[$value[0]], ' OR');
            }
            if (isset($where['MATCH'])) {
                $MATCH = $where['MATCH'];
                if (is_array($MATCH) && isset($MATCH['columns'], $MATCH['keyword'])) {
                    $where_clause .= ($where_clause != '' ? ' AND ' : ' WHERE ') . ' MATCH ("' . str_replace('.', '"."', implode($MATCH['columns'], '", "')) . '") AGAINST (' . $this->quote($MATCH['keyword']) . ')';
                }
            }
            if (isset($where['GROUP'])) {
                $where_clause .= ' GROUP BY ' . $this->column_quote($where['GROUP']);
                if (isset($where['HAVING'])) {
                    $where_clause .= ' HAVING ' . $this->data_implode($where['HAVING'], ' AND');
                }
            }
            if (isset($where['ORDER'])) {
                $rsort = '/(^[a-zA-Z0-9_\\-\\.]*)(\\s*(DESC|ASC))?/';
                $ORDER = $where['ORDER'];
                if (is_array($ORDER)) {
                    if (isset($ORDER[1]) && is_array($ORDER[1])) {
                        $where_clause .= ' ORDER BY FIELD(' . $this->column_quote($ORDER[0]) . ', ' . $this->array_quote($ORDER[1]) . ')';
                    } else {
                        $stack = array();
                        foreach ($ORDER as $column) {
                            preg_match($rsort, $column, $order_match);
                            array_push($stack, '"' . str_replace('.', '"."', $order_match[1]) . '"' . (isset($order_match[3]) ? ' ' . $order_match[3] : ''));
                        }
                        $where_clause .= ' ORDER BY ' . implode($stack, ',');
                    }
                } else {
                    preg_match($rsort, $ORDER, $order_match);
                    $where_clause .= ' ORDER BY "' . str_replace('.', '"."', $order_match[1]) . '"' . (isset($order_match[3]) ? ' ' . $order_match[3] : '');
                }
            }
            if (isset($where['LIMIT'])) {
                $LIMIT = $where['LIMIT'];
                if (is_numeric($LIMIT)) {
                    $where_clause .= ' LIMIT ' . $LIMIT;
                }
                if (is_array($LIMIT) && is_numeric($LIMIT[0]) && is_numeric($LIMIT[1])) {
                    if ($this->database_type === 'pgsql') {
                        $where_clause .= ' OFFSET ' . $LIMIT[0] . ' LIMIT ' . $LIMIT[1];
                    } else {
                        $where_clause .= ' LIMIT ' . $LIMIT[0] . ',' . $LIMIT[1];
                    }
                }
            }
        } else {
            if ($where != null) {
                $where_clause .= ' ' . $where;
            }
        }
        return $where_clause;
    }