How we move an application without stopping it
Tests come before the first change
An upgrade without tests is a guess. We begin by writing characterization tests around the flows the business cannot afford to lose: sign-in, checkout or order entry, invoicing, the main reports, scheduled jobs. Where the code is too tangled for feature tests, browser tests drive the real screens. We are not aiming for full coverage. We want enough that a framework change which alters behavior turns something red.
Upgrading Laravel one release at a time
Jumping several major releases in one go mixes hundreds of breaking changes together, and when something fails you cannot tell which one caused it. We go release by release. Laravel Shift, an automated upgrade service, handles the mechanical edits such as renamed methods, changed config files and updated skeleton code, and opens a pull request we review line by line. Then come the parts no tool can do: replacing abandoned packages, updating code that relied on removed behavior and raising the PHP release when the framework requires it. Each step ends with a green suite and a production deploy. An upgrade spread over weeks in safe slices beats one large release that nobody dares ship.
The strangler approach for legacy PHP and CodeIgniter
For a non-Laravel application we install Laravel in front of the old code. Requests reach Laravel first. Routes that have been rebuilt are served by the new code, and everything else falls through to the legacy application untouched. Both sides read the same database and share the login session, so users move between old and new pages without noticing. Module by module the old code shrinks until it can be deleted. You keep shipping features during the migration, in the new code. For CodeIgniter projects that should stay on CodeIgniter for now, legacy PHP modernization describes the lighter options.
The database is migrated, not recreated
Your data is the asset, so the schema stays in place at first. We generate a baseline migration from the existing database, then make every later change through Laravel migrations. Eloquent models are mapped onto the tables as they are, odd column names included. Structural cleanup, such as adding foreign keys, splitting overloaded tables or fixing character sets, happens later in small migrations with backfill jobs. Old password hashes are accepted at login and rehashed, so nobody is forced to reset.
Rehearsal and rollback
Every production step is rehearsed on staging with a recent copy of live data. We compare row counts and key totals before and after, time the migration so we know how long any maintenance window must be, and write down the rollback procedure. Most steps need no downtime at all. The ones that do are scheduled with you for a quiet hour.