Strip all elements from array where they occur less than twice - php

Question

I have an array like this:
[0] = 2
[1] = 8
[2] = 7
[3] = 7
And I want to end up with an array that looks like:
[0] = 7
[1] = 7
Basically, remove all elements where they occur less than twice.
Is their a PHP function that can do this?

Answer 1

try this,
$ar1=array(2,3,4,7,7);
$ar2=array();
foreach (array_count_values($ar1) as $k => $v) {
if ($v > 1) {
for($i=0;$i<$v;$i++)
{
$ar2[] = $k;
}
}
}
print_r($ar2);
output
Array ( [0] => 7 [1] => 7 )

Answer 2

Something like this would work, although you could probably improve it with array_reduce and an anonymous function
<?php
$originalArray = array(2, 8, 7, 7);
foreach (array_count_values($originalArray) as $k => $v) {
if ($v < 2) {
$originalKey = array_search($k, $originalArray);
unset($originalArray[$originalKey]);
}
}
var_dump(array_values($originalArray));

Answer 3

$testData = array(2,8,7,7,5,6,6,6,9,1);
$newArray = array();
array_walk(
array_filter(
array_count_values($testData),
function ($value) {
return ($value > 1);
}
),
function($counter, $key) use (&$newArray) {
$newArray = array_merge($newArray,array_fill(0,$counter,$key));
}
);
var_dump($newArray);
Though it'll give a strict standards warning. To avoid that, you'd need an interim stage:
$testData = array(2,8,7,7,5,6,6,6,9,1);
$newArray = array();
$interim = array_filter(
array_count_values($testData),
function ($value) {
return ($value > 1);
}
);
array_walk(
$interim,
function($counter, $key) use (&$newArray) {
$newArray = array_merge($newArray,array_fill(0,$counter,$key));
}
);
var_dump($newArray);

Answer 4

You could use a combination of array_count_values (which will give you an associative array with the value as the key, and the times it occurs as the value), followed by a simple loop, as follows:
$frequency = array_count_values($yourArray);
foreach ($yourArray as $k => $v) {
if (!empty($frequency[$v]) && $frequency[$v] < 2) {
unset($yourArray[$k]);
}
}
I did not test it, but I reckon it works out of the box. Please note that you will loop over your results twice and not N^2 times, unlike an array_search method. This can be further improved, and this is left as an exercise for the reader.

Answer 5

This was actually harder to do than i thought...anyway...
$input = array(2, 8, 7, 7, 9, 9, 10, 10);
$output = array();
foreach(array_count_values($input) as $key => $value) {
if ($value > 1) $output = array_merge($output, array_fill(0, $value, $key));
}
var_dump($output);

Answer 6

$arrMultipleValues = array('2','3','5','7','7','8','2','9','11','4','2','5','6','1');
function array_not_unique($input)
{
$duplicatesValues = array();
foreach ($input as $k => $v)
{
if($v>1)
{
$arrayIndex=count($duplicatesValues);
array_push($duplicatesValues,array_fill($arrayIndex, $v, $k));
}
}
return $duplicatesValues;
}
$countMultipleValue = array_count_values($arrMultipleValues);
print_r(array_not_unique($countMultipleValue));

Answer 7

Is their [sic!] a PHP function that can do this?
No, PHP has no built-in function (yet) that can do this out of the box.
That means, if you are looking for a function that does this, it needs to be in PHP userland. I would like to quote a comment under your question which already suggest you how you can do that if you are looking for that instead:
array_count_values() followed by a filter with the count >1 followed by an array_fill() might work
By Mark Baker 5 mins ago
If this sounds a bit cryptic to you, those functions he names are actually built-in function in PHP, so I assume this comes most close to the no, but answer:
array_count_values()
array_fill()

Answer 8

This does the job, maybe not the most efficient way. I'm new to PHP myself :)
<?php
$element = array();
$element[0] = 2;
$element[1] = 8;
$element[2] = 7;
$element[3] = 7;
$count = array_count_values($element);
var_dump($element);
var_dump($count);
$it = new RecursiveIteratorIterator( new RecursiveArrayIterator($count));
$result = array();
foreach ($it as $key=>$val){
if ($val >= 2){
for($i = 1; $i <= $val; $i++){
array_push($result,$key);
}
}
}
var_dump($result);
?>
EDIT: var_dump is just so you can see what's going on at each stage