Removing duplicate items from array but merging duplicate keys

Question

This is one of those situations where I'm sure that there's a simple solution, and I need help getting to it.

Suppose we're dealing with three phone numbers: home (h), office (o) and mobile (m). We need to avoid displaying duplicate phone numbers to the end user.

To better explain, here are three sample cases (in PHP):

Case 1:

$phone = array(
    'h' => '212-555-1212',
    'o' => '212-555-1212',
    'm' => '212-555-1212'
);

Should yield:

212-555-1212 (h,o,m)

Case 2:

$phone = array(
    'h' => '212-555-1212',
    'o' => '212-555-1234', // different
    'm' => '212-555-1212'
);

Should yield:

212-555-1212 (h,m)
212-555-1234 (o)

Case 3:

$phone = array(
    'h' => null,
    'o' => '212-555-1234',
    'm' => '212-555-1212'
);

Should yield:

212-555-1234 (o)
212-555-1212 (m)

I have tried using various case statements, by checking for each scenario, but it's complicated by the fact that some values might be empty. I have also tried using overly-complicated if/elseif/else conditions, but again, it's extremly inelegant.

My best efforts resulted from using array_filter to remove empty elements from the array and the using array_unique to remove duplicates, but then I lose the H/O/M key:

$phone = array_filter(array_unique($phone));

How should I approach this?

jszobody · Accepted Answer · 2016-03-12 01:26:08Z

3

I would first flip the array. Create a new array with the phone number as the key. Something like this:

$numbers = [];
foreach($phone AS $type => $number) { 
    $numbers[$number][] = $type;
}

Now you have a $numbers array, with unique phones, and an array of types for each one.

To display your output then:

foreach($numbers AS $number => $types) {
    echo $number . " (" . implode(",",$types) . ")";
}

I've wrapped this up as a real quick function, and run all three of your cases through. You can see the code and output here:

https://3v4l.org/U6c4K

edited Mar 12, 2016 at 1:26

answered Mar 12, 2016 at 1:11

jszobody

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1 Comment

pbarney Over a year ago

Creative thinking! Thank you, I'll keep this one in my toolbox.

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