how do i know PHQL builtin functions

how do i know PHQL builtin functions, i find in documents, but nothing

PHQL is pretty much SQL but with a small Phalcon twist. For instance:

SELECT id, name FROM users WHERE id = 1

in PHQL is

SELECT id, name FROM \MyNamespace\Users WHERE id = :id:

where the bound parameter is 1.

What functions are you looking for?