Memorising the manual is the strategy of a surface learner. Surface learners can make pretty good PHP programmers, but they'll struggle with, say, passing Javascript closures.
A deep learner will look for the underlying principles and abstractions. They can quickly get an overview that, even when it's fuzzy, is still accurate enough for them to know where the gaps in their knowledge are, so they can fill those gaps quickly when they need to. They're like Mendeleev with his first periodic table. He didn't need somebody to show him a sample of gallium to know that it existed: he could inferred its presence and properties from the overall structure of the system.
Of course, a really advanced programmer will have done both. They will know and understand everything. But those guys are few and far between.