Search Multiple Arrays for - php

Question

I have officially hit a wall and I cannot figure out the solution to this issue. Any help would be much appreciated! I have tried array_intersect() but it just keeps running against the first array in the function, that wont work.
I have an infinite amounts of arrays (I'll show 4 for demonstration purposes), for example:
// 1.
array(1,2,3,4,5);
// 2.
array(1,3,5);
// 3.
array(1,3,4,5);
// 4.
array(1,3,5,6,7,8,9);
I need to figure out how to search all the arrays and find only the numbers that exist in all 4 arrays. In this example I need to only pull out the values from the arrays - 1, 3 & 5.
PS: In all reality, it would be best if the function could search against a multi dimensional array and extract only the numbers that match in all the arrays within the array.
Thanks so much for your help!

Answer 1

Fun question! This worked:
function arrayCommonFind($multiArray) {
$result = $multiArray[0];
$count = count($multiArray);
for($i=1; $i<$count; $i++) {
foreach($result as $key => $val) {
if (!in_array($val, $multiArray[$i])) {
unset($result[$key]);
}
}
}
return $result;
}
Note that you can just use $multiArray[0] (or any sub-array) as a baseline and check all the others against that since any values that will be in the final result must necessarily be in all individual subarrays.

Answer 2

How about this?
Find the numbers that exist in both array 1 and 2. Then compare those results with array 3 to find the common numbers again. Keep going as long as you want.
Is this what you are getting at?

Answer 3

If it's in a multidimensional array you could
$multiDimensional = array(/* Your arrays*/);
$found = array_pop($multiDimensional);
foreach($multiDimensional as $subArray)
{
foreach($found as $key=>$element)
{
if(!in_array($element, $subArray)
{
unset($found[$key]);
}
}
}

Answer 4

Per your comment on my other question here is a better solution:
<?php
// 1. merge the arrays
$merged_arrays = array_merge( $arr1, $arr2, $arr3, $arr4, ...);
// 2. count the values
$merged_count = array_count_values( $merged_arrays );
// 3. sort the result for elements that only matched once
for( $merged_count as $key => $value ){
if ($value == 1) {
// 4. unset the values that didn't intersect
unset($merged_count($key));
}
}
// 5. print the resulting array
print_r( $merged_count );

Answer 5

Performing iterated in_array() calls followed by unset() is excessive handling and it overlooks the magic of array_intersect() which really should be the hero of any solid solution for this case.
Here is a lean iterative function:
Code: (Demo)
function array_intersect_multi($arrays){ // iterative method
while(sizeof($arrays)>1){
$arrays[1]=array_intersect($arrays[0],$arrays[1]); // find common values from first and second subarray, store as (overwrite) second subarray
array_shift($arrays); // discard first subarray (reindex $arrays)
}
return implode(', ',$arrays[0]);
}
echo array_intersect_multi([[1,2,3,4,5],[1,3,5],[1,3,4,5],[1,3,5,6,7,8,9]]);
// output: 1, 3, 5
This assumes you will package the individual arrays into an indexed array of arrays.
I also considered a recursive function, but recursion is slower and uses more memory.
function array_intersect_multi($arrays){ // recursive method
if(sizeof($arrays)>1){
$arrays[1]=array_intersect($arrays[0],$arrays[1]); // find common values from first and second subarray, store as (overwrite) second subarray
array_shift($arrays); // discard first subarray (reindex $arrays)
return array_intersect_multi($arrays); // recurse
}
return implode(', ',$arrays[0]);
}
Furthermore, if you are happy to flatten your arrays into one with array_merge() and declare the number of individual arrays being processed, you can use this:
(fastest method)
Code: (Demo)
function flattened_array_intersect($array,$total_arrays){
return implode(', ',array_keys(array_intersect(array_count_values($array),[$total_arrays])));
}
echo flattened_array_intersect(array_merge([1,2,3,4,5],[1,3,5],[1,3,4,5],[1,3,5,6,7,8,9]),4);
or replace array_intersect() with array_filter() (slightly slower and more verbose):
function flattened_array_intersect($array,$total_arrays){
return implode(', ',array_keys(array_filter(array_count_values($array),function($v)use($total_arrays){return $v==$total_arrays;})));
}
echo flattened_array_intersect(array_merge([1,2,3,4,5],[1,3,5],[1,3,4,5],[1,3,5,6,7,8,9]),4);