Filter out duplicate values in array using php

Question

Please help me to filter out only duplicate values in array using php.Consider,

$arr1 = array('php','jsp','asp','php','asp')

Here I would prefer to print only

array('php'=>2,
       'asp'=>2)

tried it by

print_r(array_count_values($arr1));

but, its getting count of each element.

It's getting the count of each element... so what's it doing wrong? — BoltClock
– BoltClock, Commented Aug 27, 2010 at 11:12
Ah, I do now. There's not an easy way to do this: BoltClock's approach is probably best. — Pekka
– Pekka, Commented Aug 27, 2010 at 11:16
I figured it out. OP is asking to only filter out the keys which are reported as having duplicates in $arr1. — BoltClock
– BoltClock, Commented Aug 27, 2010 at 11:16

BoltClock · Accepted Answer · 2010-08-27 11:22:55Z

7

OK, after the comments and rereading your question I got what you mean. You're still almost there with array_count_values():

$arr1 = array('php','jsp','asp','php','asp');
$counts = array_count_values($arr1);

You just need to remove the entries that are shown as only occurring once:

foreach ($counts as $key => $val) {
    if ($val == 1) {
        unset($counts[$key]);
    }
}

EDIT: don't want a loop? Use array_filter() instead:

// PHP 5.3+ only
$counts = array_filter($counts, function($x) { return $x > 1; });

// Older versions of PHP
$counts = array_filter($counts, create_function('$x', 'return $x > 1;'));

edited Aug 27, 2010 at 11:22

answered Aug 27, 2010 at 11:14

BoltClock

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4 Comments

Codeacula Over a year ago

Just like the one I was just typing. I'd like to add, though, if the array is large enough, they should set a counter and use a for loop.

BoltClock Over a year ago

@Ajith: included a non-loop solution.

Leon Over a year ago

You can use array_filter with a callback function that checks if the value is 1 if you really don't want to (write a) loop.

salathe Over a year ago

Your callbacks to array_filter don't check the value of $x.

salathe · Accepted Answer · 2010-08-27 11:32:28Z

5

If you don't want the counts, a simpler way would be to do:

$arr1 = array('php','jsp','asp','php','asp');
$dups = array_diff_key($arr1, array_unique($arr1));

answered Aug 27, 2010 at 11:32

salathe

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