PHP: Check for duplicate values in a multidimensional array - php

Question

I have this issue with multidimensional arrays.
Given the following multidimensional array:
Array(
[0] => Array("a", "b", "c")
[1] => Array("x", "y", "z")
[2] => Array("a", "b", "c")
[3] => Array("a", "b", "c")
[4] => Array("a", "x", "z")
)
I want to check its values and find duplicates (i.e. keys 0, 2 and 3) leaving just one key - value pair deleting the others, resulting in somthing like this:
Array(
[0] => Array("a", "b", "c")
[1] => Array("x", "y", "z")
[2] => Array("a", "x", "z")
)
How can I do that??

Answer 1

This will remove duplicate items from your array using array_unique():
$new_arr = array_unique($arr, SORT_REGULAR);

Answer 2

You can simply do it using in_array()
$data = Array(
0 => Array("a", "b", "c"),
1 => Array("x", "y", "z"),
2 => Array("a", "b", "c"),
3 => Array("a", "b", "c"),
4 => Array("a", "x", "z"),
);
$final = array();
foreach ($data as $array) {
if(!in_array($array, $final)){
$final[] = $array;
}
}
which will get you something like
array(3) {
[0] => array(3) {
[0] => string(1) "a"
[1] => string(1) "b"
[2] => string(1) "c"
}
[1] => array(3) {
[0] => string(1) "x"
[1] => string(1) "y"
[2] => string(1) "z"
}
[2] => array(3) {
[0] => string(1) "a"
[1] => string(1) "x"
[2] => string(1) "z"
}
}

Answer 3

You can go smart with serialization for comparison of arrays.
var_dump(makeUnique($data));
function makeUnique(array $data)
{
$serialized = array_map(create_function('$a', 'return serialize($a);'), $data);
$unique = array_unique($serialized);
return array_intersect_key($unique, $data);
}
Have fun

Answer 4

$arr = ...;
$final = array();
sort($arr);
foreach ($arr as $el) {
if (!isset($prev) || $el !== $prev)
$final[] = $el
$prev = $el;
}
This is a more efficient1 solution (log n + n instead of quadratic) but it relies on a total order between all the elements of the array, which you may not have (e.g. if the inner arrays have objects).
1 More efficient than using in_array. Turns out array_unique actually uses this algorithm, so it has the same shortcomings.

Answer 5

To check using array_unique on multidimensional arrays, you need to flatten it out like so, using implode.
$c=count($array)
for($i=0;$i<$c;$i++)
{
$flattened=implode("~",$array[$i]);
$newarray[$i]=$flattened;
}
if(count(array_unique($newarray)
<count($newarray))
{
//returns true if $array contains duplicates
//can also use array_unique on $newarray
//to remove duplicates, then explode,
//to return to default state
}
Hope this is helpful, took sometime to get it.

Answer 6

**This is example array**
$multi_com=[
[
{
"combination_id": "19"
},
{
"combination_id": "20"
},
{
"combination_id": "21"
}
],
[
{
"combination_id": "18"
},
{
"combination_id": "20"
},
{
"combination_id": "22"
}
],
[
{
"combination_id": "20"
},
{
"combination_id": "21"
}
]
]
**This is sample code**
$array1 = [];
$array2 = [];
$status = false;
foreach ($multi_com as $key => $val) {
foreach ($val as $key2 => $val2) {
if (count($array1) !== 0) {
$array_res = in_array($val2->combination_id, $array1);
if ($array_res) {
$array2[] = $val2->combination_id;
}
}
}
if (!$status) {
for ($x = 0; $x < count($val); $x++) {
$array1[] = $val[$x]->combination_id;
}
} else {
$array1 = [];
$array1 = $array2;
$array2 = [];
}
$status = true;
}
return $array1;