The Heartbeat API keeps post locks and autosave working by posting to admin-ajax.php on a timer — every fifteen seconds in the editor, every sixty elsewhere in the…
Before 5.2 the HTTP kernel had one global middleware stack, so anything needed by web routes also ran for API routes — sessions, CSRF verification and cookie encryption…
Xdebug instruments every function call, so it sees everything and multiplies the runtime by three to five. A sampling profiler interrupts periodically and records the stack, so it…
Deploying by rsync on a Friday afternoon, and what replaced it: lint, test, build, stage, promote — with a rollback that is the same mechanism rather than a…
Applying several regular expressions with different callbacks meant chaining preg_replace_callback() calls, each re-scanning the whole subject — three patterns, three passes. Patterns are applied in the order given…
Sending a webhook or writing an analytics row after the page has rendered still holds the connection open, because PHP does not close it until the script ends.…
WooCommerce maintains its own session handler backed by a database table and a cookie, entirely separate from $_SESSION. Code that starts a PHP session to store something cart-related…
A stylesheet in the head blocks rendering until it has loaded, and a script without defer blocks parsing until it has executed. Both are correct behaviour and both…
Every request to admin-ajax.php loads the full admin bootstrap before reaching your handler — a measurable amount of work for an endpoint that returns three fields, and it…
class introduced no new object model. It is syntax over the prototype chain, which explains most of the behaviour that surprises people coming from other languages. Methods are…