Hooks (both actions and filters) run callbacks in ascending priority order. Lower numbers are executed first. Callbacks with the same priority run in the order they were added.
See also: Actions and Filters.
How Priorities Work
- Default priority is 10.
- Smaller numbers run earlier; larger numbers run later.
- When priorities are equal, callbacks execute FIFO (first added, first run).
Example (Actions)
addAction('order.placed', fn () => logger('A: priority 5'), 5);
addAction('order.placed', fn () => logger('B: priority 10'));
addAction('order.placed', fn () => logger('C: priority 20'), 20);
Execution order: A, B, C.
Example (Filters)
addFilter('title.display', fn ($title) => strtoupper($title), 5);
addFilter('title.display', fn ($title) => $title.'!');
$result = applyFilters('title.display', 'Hello');
// 'HELLO!'
Tips
- Reserve low numbers (e.g., 1–5) for foundational work.
- Keep defaults at 10 for most extensions.
- Use higher numbers (20+) for "final touches".
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