PHP Easy way to compare two arrays: Same values, regardless of order

Question

Just a note of previous research on SO:

search under "[php] array sort" (15,000 results)
compare two arrays where values are not in same order (does not cleanly address direct issue)
Compare two associative arrays regarding the order of keys (different issue)

At least I believe that:

Given the example:

$arr1 = [21, 23, 25];
$arr2 = [25, 21, 23];

It the easiest, nondestructive manner to compare these for equal values, regardless of order

$arr1s = $arr1;
$arr2s = $arr2;

sort($arr1s, SORT_NUMERIC);
sort($arr2s, SORT_NUMERIC);

$isSameValues = ($arr1s === $arr2s);

Or is there an easier, cleaner way to do this?

See the first answer: stackoverflow.com/questions/4519847/… — hlscalon
– hlscalon, Commented Jun 25, 2014 at 17:06
1nflktd: Not sure if you meant the answer posited in the question of the first response. I need to streamline as best I can due to the hit that this is going to take. I have no option but to be making this call a metric $&%*tonne of times. :-/ — Dru Freeman
– Dru Freeman, Commented Jun 25, 2014 at 19:14

FuzzyTree · Accepted Answer · 2017-03-07 05:41:11Z

4

Use array_count_values, which is O(n) vs O(n log n) for sorting

$a = [1, 1, 3, 2];
$b = [1, 2, 2, 3];
var_dump (array_count_values($b) == array_count_values($a)); //false

Note: this only works with arrays where all values are strings or ints.

edited Mar 7, 2017 at 5:41

answered Jun 25, 2014 at 17:00

FuzzyTree

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6 Comments

hlscalon Over a year ago

Note that something like this $a = [33];$b = [33, 3.3, 2.1]; would return true. Example: ideone.com/EytqqR

hlscalon Over a year ago

yes, but I really liked your answer, and I know that someone will see this in the future and will try to compare with floats and will complain about it, so I'm just informing already :p

FuzzyTree Over a year ago

@1nflktd fair enough, added a note to clarify the limitation :)

Dru Freeman Over a year ago

FuzzyTree: Are you saying that the array_count_values is O(n) and the double copy and sort being O(n long n)? If so, then I will try this as my lists are ALWAYS ints and should NEVER have duplicates. (Should being the operative term)

FuzzyTree Over a year ago

@LordAndrei each array_count_values is O(n) whereas each sort is O(n log n), to be clear array_count_values handles duplicates correctly. my note about duplicates was regarding array_diff

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clami219 · Accepted Answer · 2014-06-25 17:03:10Z

0

You were very near to the right solution! Here is your code fixed:

$arr1 = [21, 23, 25];
$arr2 = [25, 21, 23];

$arr1s = $arr1;
$arr2s = $arr2;

sort($arr1s, SORT_NUMERIC);
sort($arr2s, SORT_NUMERIC);

$isSameValues = ($arr1 == $arr2);

See it working here: http://sandbox.onlinephpfunctions.com/code/b737d3a9cf45e077a0d1f2c0195f389b81ace4a3

If the two arrays have same keys and values, a == is enough, as shown here:

enter image description here

answered Jun 25, 2014 at 17:03

clami219

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