Using PHP's array_reverse() on an array of arrays, getting odd behaviour. Why?

Question

So, array_reverse() is supposed to take an array, and return a copy of it with elements in reverse order, and it's always been working faithfully for me, up until today. I have an array of arrays, and I need to get them in reverse order, so I'd assumed array_reverse would do exactly what I needed, but it seems to be behaving oddly, and I can't figure out why.

My initial array (yes, I'm doing some HTML parsing):

Array(
    0 => Array(
        0 => '<blockquote',
        1 => int 232
    ),
    1 => Array(
        0 => '<blockquote',
        1 => int 593
    ),
    2 => Array(
        0 => '<blockquote',
        1 => int 938
    ),
    3 => Array(
        0 => '</blockquote',
        1 => int 2627
    ),
    4 => Array(
        0 => '</blockquote',
        1 => int 2758
    ),
    5 => Array(
        0 => '</blockquote',
        1 => int 2794
    ),
)

running array_reverse($arr) on it, one would expect the returned array to be:

Array (
    0 => Array(
        0 => '</blockquote',
        1 => int 2794
    ),
    1 => Array(
        0 => '</blockquote',
        1 => int 2758
    ),
    2 => Array(
        0 => '</blockquote',
        1 => int 2627
    ),
    3 => Array(
        0 => '<blockquote',
        1 => int 938
    ),
    4 => Array(
        0 => '<blockquote',
        1 => int 593
    ),
    5 => Array(
        0 => '<blockquote',
        1 => int 232
    ),
)

However, it returns an unaltered array. Now, if I do array_reverse($arr[0]), then it reverses the entire array like I want.

I can think of no reason it would not be reversing the initial array, and why, when passing a specific key, it would reverse the entire array, rather than that one sub-array. Why would it be doing this?

EDIT: I walked away and came back, looked at it, and realized the main array had a single element which was the array I'd posted above. Just a good ol' ID-10-T error.

Can you create an example test case (e.g. on codepad) which shows the behaviour? — cmbuckley
– cmbuckley, Commented Apr 5, 2012 at 17:03
"yes, I'm doing some HTML parsing" Nice fending of the shit storm ;) — PeeHaa
– PeeHaa, Commented Apr 5, 2012 at 17:04
I walked away from it for a few minutes and came back, and realized I'm an idiot. I somehow completely missed seeing the extra array level at the beginning, so now it makes sense. — Tarka
– Tarka, Commented Apr 5, 2012 at 17:09

PeeHaa · Accepted Answer · 2012-04-05 17:06:20Z

1

However, it returns an unaltered array.

It should just work.

Now, if I do array_reverse($arr[0]), then it reverses the entire array like I want.

Are you sure you don't have an extra level in your array?? I'm pretty sure you have an extra level!

answered Apr 5, 2012 at 17:06

PeeHaa

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1 Comment

Tarka Over a year ago

Yup! Just looking at it more closely (stepped away for a few minutes came back) and indeed I do! I don't know how I missed seeing this, and I feel like an idiot.

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