priorities and execution order

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title: Priorities and Execution Order

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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