Check if array elements are in a different array

Question

I'm trying to create a function to return true if all items in $array1 are in $array2, if not return false.

What I'm trying to do:

$array1 = ['1', '3', '9', '17'];
$array2 = ['1', '2', '3', '4', '9', '11', '12', '17'];

function checkArray($arr, $arr2) {
    If all elements in $arr are in $arr2 return true
    else return false
}

if (checkArray($array1, $array2) {
    // Function returned true
} else {
    // Function returned false
}

I can't think of how to do this! Help much appreciated.

SOLUTION:

function checkArray($needles, $haystack) {
    $x = array_diff($needles, $haystack);
    if (count($x) > 0) {
        return false;
    } else {
        return true;
    }
}
// Returns false because more needles were found than in haystack
checkArray([1,2,3,4,5], [1,2,3]); 
// Returns true because all needles were found in haystack
checkArray([1,2,3], [1,2,3,4,5]);

Didn't know about this, feel like an eejit now lol :) thanks for the help! — David C
– David C, Commented Mar 26, 2013 at 21:08

000 · Accepted Answer · 2013-03-26 21:04:02Z

2

function checkArray($arr, $arr2) {
    return !count(array_diff($arr, $arr2));
}

array_diff: Returns an array containing all the entries from $arr that are not present in $arr2. http://php.net/manual/en/function.array-diff.php

answered Mar 26, 2013 at 21:04

000

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1 Comment

David C Over a year ago

Didn't find this when searching!! Ahh you're a legend, good man cheers!

alxgb · Accepted Answer · 2013-03-26 21:11:36Z

1

I'm not really sure as to how array_diff is useful in any way. So who cares if there are diferences? You are not comparing arrays, or at least that's not what I understand in the question. You want to know if one array contains the other.

PHP has a handy function for that

function checkArray($arr, $arr2) {
    return (array_intersect($arr, $arr2) == $arr);
}

answered Mar 26, 2013 at 21:11

alxgb

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6 Comments

David C Over a year ago

Now you've confused me... Gonna give this array_diff a try. I also got my problem solved in a totally different way but definitely far from the best solution!

alxgb Over a year ago

array_dif will give you an array containing differences. But you want to know if one array values are contained in the other, right? Running array_diff just by itself won't give you much.

David C Over a year ago

Well if the count of the differences is greater than zero then not everything in $array1 was found in $array2. Or at least that's how I'm interpreting it! either way both have taught me something new :)

000 Over a year ago

@Think array_diff([1,2,3],[1,2,3,4]) is empty. It won't return that [4].

alxgb Over a year ago

@joeframbach Of course not, why would I? (Plus don't have priviledges for that yet). I did try array_diff and it turns out it doesn't work exactly as I expected. Thanks for the clarification.

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