ElephpantDB: Full SQL Database in One PHP File

Overview

ElephpantDB is an experimental SQL database implemented in a single PHP file by Anton Medvedev. It provides a complete SQL engine capable of creating tables, querying, updating, and deleting data, all within a standalone PHP script that runs on PHP 8.3 or later (64-bit required). The project is available on GitHub at https://github.com/antonmedv/elephpantdb.

Supported SQL Features

CREATE TABLE

, SELECT, UPDATE, DELETE Indexes (hash-based) INSERT with prepared parameters

Sorting ( ORDER BY) and limiting ( LIMIT)

Storage Architecture

Data rows are stored in an append-only heap where each record is identified by its byte offset. Updates write a new version of the row; deletes mark the old record as stale. A VACUUM command eventually reclaims space by cleaning up historical versions.

Indexing and Reliability

The heap remains the source of truth, while indexes are treated as rebuildable caches. This design provides a healthy balance: the heap stores facts, and indexes accelerate lookups without guaranteeing absolute correctness. The engine also includes file locking, checksums, and crash recovery to ensure durability.

Usage Options

ElephpantDB can be used directly from PHP code or exposed as a JSON-over-HTTP endpoint. The HTTP interface accepts SQL statements and parameters via POST requests, with optional token authentication for basic access control.

Requirements and Design Philosophy

The engine requires PHP 8.3+ (64-bit). The single-file distribution is partly for convenience and partly because splitting the engine into modules was considered too adventurous and irresponsible at this experimental stage.

Production Readiness

The author advises against migrating large production systems to ElephpantDB at version 0.1.0. It is suitable for storing a few important records or unlimited unimportant data, and serves as an educational example of a database engine written in PHP.