PHP: one dimensional array to multidimensional array with element multiplication - php

Question

Is there an easy way to transform a one dimensional array into multidimensional array and along with that add a certain element to the newly created sub-arrays?
The countrycode always has 2 digits and appears only once before a set of locations. That's the element that I'd like to duplicate and add it to every subarray as shown below.
Thanks in advance!
That's what I have:
0 => AT
1 => Vienna-S03-I01
2 => 28 Users
3 => Vienna-S03-I02
4 => 25 Users
5 => Vienna-S03-I03
6 => 24 Users
7 => AU
8 => Sydney-S01-I01
9 => 45 Users
10 => BE
11 => Brussels-S01-I01
12 => 30 Users
13 => Brussels-S01-I02
14 => 37 Users
That's what I'd like to have:
0 =>
0 => AT
1 => Vienna-S03-I01
2 => 28 Users
1 =>
0 => AT
1 => Vienna-S03-I02
2 => 25 Users
2 =>
0 => AT
1 => Vienna-S03-I03
2 => 24 Users
3 =>
0 => AU
1 => Sydney-S01-I01
2 => 45 Users
4 =>
0 => BE
1 => Brussels-S01-I01
2 => 30 Users
5 =>
0 => BE
1 => Brussels-S01-I02
2 => 37 Users

Answer 1

If there is a guarantee that array will always follow rule you demonstrated, then code is below. Otherwise few condition check should be added there to make sure that we have proper value type in every given $item.
$array = ['AT',
'Vienna-S03-I01',
'28 Users',
'Vienna-S03-I02',
'25 Users',
'Vienna-S03-I03',
'24 Users',
'AU',
'Sydney-S01-I01',
'45 Users',
'BE',
'Brussels-S01-I01',
'30 Users',
'Brussels-S01-I02',
'37 Users'];
$code='none';
$result=[];
$resIndex=-1;
$swing=false;
foreach($array as $item){
if (strlen($item)===2){
$code=$item;
}else{
if ($swing===false){
$resIndex++;
$result[$resIndex][]=$code;
}
$result[$resIndex][]=$item;
$swing=!$swing;
}
}
print_r($result);
?>

Answer 2

This is a very light method in terms of function calls and variables. isset() is a very swift function call, so there will be minimal drag there. The snippet is condensed by declaring multiple variables in a single line ($result[++$i][]=$k=$v;) and by incrementing the counter (++$i) inside of the result array declarations.
Code: (Demo)
$array = ['AT',
'Vienna-S03-I01',
'28 Users',
'Vienna-S03-I02',
'25 Users',
'Vienna-S03-I03',
'24 Users',
'AU',
'Sydney-S01-I01',
'45 Users',
'BE',
'Brussels-S01-I01',
'30 Users',
'Brussels-S01-I02',
'37 Users'];
$i=-1;
foreach($array as $v){
if(strlen($v)==2){ // check for new Country ID
$result[++$i][]=$k=$v; // preserve Country ID as $k, store as a new batch
}else{
if(isset($result[$i][2])){ // when three elements in current batch, start new...
$result[++$i][]=$k; // increment counter and store preserved Country ID
}
$result[$i][]=$v; // add $v to batch
}
}
var_export($result);
p.s. as a matter of further micro-optimization, you could swap out strlen() for another isset() call -- but that is a bit less intuitive:
$i=-1;
foreach($array as $v){
if(!isset($v[2])){ // check for existence of character at offset 2
$result[++$i][]=$k=$v;
}else{
if(isset($result[$i][2])){
$result[++$i][]=$k;
}
$result[$i][]=$v;
}
}
This is a functional approach that doesn't need to iterate for each element in the array. I just love array_splice() and its fantastic dual action of extracting elements and shortening the input array:
// array_splice modifies the original array (shortens it) and returns the removed elements
while($array){
if(strlen($array[0])==2){ // if the first value is a Country id
$id=$array[0]; // preserve id
$result[]=array_splice($array,0,3); // cut away and preserve first three elements
}else{
$result[]=[$id]+array_splice($array,0,2); // store id and first two elements
}
}
var_export($result);
...and finally, my DRYest method:
while($array){
if(strlen($array[0])==2){ // if the first value is a Country id
$id=array_splice($array,0,1);
}
$result[]=array_merge($id,array_splice($array,0,2)); // store preserved id and two elements
}
var_export($result);