Question

As we know, there are four functions that can be used to insert into and delete from an array:

1. array_push()
2. array_pop()
3. array_unshift()
4. array_shift()

What’s the meaning of array_unshift() and array_shift(), I mean why they are named like this?

Answer 1

It’s historical. Whereas in newer languages we probably wouldn’t call it “shift” any more, older terminology from Perl includes the shift keyword, whose job is to:

[Shift] the first value of the array off and returns it, shortening the array by 1 and moving everything down.

This is often used with the @_ array, which contains function arguments, and shift would provide access to them one at a time.

PHP, in its early days when Perl was still widely used for web programming, has simply taken this terminology, added the “inverse” unshift and left it.

Another example is glob, which is named after the libc glob() function. I imagine the intent was to make these functions familiar to those coming to PHP from existing languages, but in retrospect a decade or so later, perhaps the terms have aged poorly.