php remove duplicates based on first value of multidimensional array

Question

Given

[0] => Array
    (
        [0] => ask.com
        [1] => 2320476
    )

[1] => Array
    (
        [0] => amazon.com
        [1] => 1834593
    )

[2] => Array
    (
        [0] => ask.com
        [1] => 1127456
    )

I need to remove duplicate values solely based on first value, regardless of what any other subsequent values may be. Notice [0][1] differs from [2][1] yet I consider this as a duplicate because there are two matching first values. The other data is irrelevant and shouldn't be considered in comparison.

No, it's not quite the same...notice [0][1] differs from [2][1]. This is not an exact match therefore it will not be removed. I will update the question to specify this. — Jared Eitnier
– Jared Eitnier, Commented Dec 17, 2012 at 21:45
Only $newList = array_map("unserialize", array_unique(array_map("serialize", $newList))); however this is only for comparing exact matches. It doesn't work in my case. — Jared Eitnier
– Jared Eitnier, Commented Dec 17, 2012 at 21:50
Have you made an attempt to solve this yourself? Look at the other solutions; try mould your own and post it asking for help :) — purpletree
– purpletree, Commented Dec 17, 2012 at 21:50

Stegrex · Accepted Answer · 2012-12-17 21:50:45Z

4

Try this, assuming that $mainArray is the array you have.

$outputArray = array(); // The results will be loaded into this array.
$keysArray = array(); // The list of keys will be added here.
foreach ($mainArray as $innerArray) { // Iterate through your array.
    if (!in_array($innerArray[0], $keysArray)) { // Check to see if this is a key that's already been used before.
        $keysArray[] = $innerArray[0]; // If the key hasn't been used before, add it into the list of keys.
        $outputArray[] = $innerArray; // Add the inner array into the output.
    }
}
print_r($outputArray);

answered Dec 17, 2012 at 21:50

Stegrex

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3 Comments

Jared Eitnier Over a year ago

This appears to work how I need it to...obviously not knowing a ton of comparison methods, is this as clean as it gets?

Jared Eitnier Over a year ago

Oh and I would give another +1 for the commenting :) Thank you!

Francesco Over a year ago

what about if you have three columns for each row?

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