When we reach for it
Existing PHP applications, and migrations off them. Modern PHP with typed properties and a real dependency manager is a considerably better language than its reputation, and a working system is worth more than an elegant rewrite.
When we would argue against it
We do not propose it for new work. Where a rebuild genuinely is the right call, we will say what it costs and what it risks first — most requests for a rewrite are really requests for a boundary and a test suite.
What it looks like in delivery
Strangler-pattern migrations, mainly: put the new system in front, move one route at a time, and keep the old application serving everything that has not moved yet, so there is never a weekend where everything changes at once.