How to Make array_diff ignore One Value in PHP

Question

If you do an array_diff between two values:

$ignore = array_diff($arr1, $arr2);

How can you make it avoid removing one specific value from $arr1?

Don't Panic · Accepted Answer · 2016-01-20 22:03:04Z

1

Here are two arrays for example.

$arr = ['something', 'another thing', 'three things'];
$arr = ['something', 'another thing', 'different thing'];

And the value you want to keep:

$keep = 'something';

If you need that certain value to always be there, it probably would be easiest to just explicitly add it after doing the diff.

$ignore = array_diff($arr1, $arr2);
$ignore[] = $keep;

but if you only need it to not be removed if it is present, then you can use array_udiff.

$ignore = array_udiff($arr1, $arr2, function($a, $b) use ($keep) {
    if ($a == $keep) return -1;
    return $a == $b ? 0 : 1;
});

answered Jan 20, 2016 at 22:03

Don't Panic

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