1

There are probably lots of array questions. But I couldn't find one that answered this specific problem:

I have an associative array as a result from a database query. I loop trough it with a foreach loop. One of the columns contains a number. If that number is larger than 1, I have to duplicate that row x number of times so that the array will have x similiar rows.

I wonder how to do this?

foreach( $db_rows as $key => $value )
{  
  if( $value["number"] > 1 )
  //DUPLICATE $value and insert x number of times into $db_rows directly after $key.  
}
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10
  • what is x or n? Commented Jun 7, 2019 at 10:10
  • I assume $db_rows is a numerical array since you say you want it inserted directly after $key? Commented Jun 7, 2019 at 10:11
  • X can be 2 or 6, basically a small INT. Commented Jun 7, 2019 at 10:15
  • Yes $db_rows has numerical keys. Commented Jun 7, 2019 at 10:15
  • into $db_rows directly after $key. this to mean you want to insert rows directly after the $key row in the DB? Commented Jun 7, 2019 at 10:16

3 Answers 3

Reset to default
4

You could declare an empty array before the foreach loop, then populate it thanks to the original, its items' number property and a for loop:

$clone_db_rows = [];

foreach( $db_rows as $key => $value )
{  
    for ($i = 0; $i < $value['number']; $i++) {
        $clone_db_rows[] = $value;
    }
}

Test it here.

@Andreas suggests using array_fill to avoid the nested for statement.

He's right, and you could do this the following way, with array_merge:

$clone_db_rows = [];

foreach( $db_rows as $key => $value )
{  
    $clone_db_rows = array_merge(
        $clone_db_rows,            // Merge the current array with... 
        array_fill(                // ...a newly created one containing...
            0,
            $value['number'],      // ... X items equals to...
            $value                 // ... $value.
        )
    );
}

Test it here.

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7 Comments

I mean.. great, but how does this insert into the db after $key whilst maintaining/fixing the incrementation?
Array_fill could remove a loop
@treyBake - The question is about altering an array, not about inserting into the datatabase (or I misread the author's post).
@KévinBibollet check comment chain (unless OP misunderstood me xD)
@treyBake - I think you misunderstood each other comment (you talked about BD, he talked about array only), but let's wait the autor's answer. ;)
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0

Probably something like this :

foreach ($db_rows as $key => $value) {
    if ($value['number'] > 1) {
        for ($i = 0; $i < $value['number'] - 1; $i++) {
            $db_rows[] = $value;
        } 
    } 
}
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4 Comments

This doesn't answer the question, he said he wants the values inserted directly after $key
This also increases number of elements in array and finding another $value['number'] in later elements will add them again, and again and again. So this foreach never stops.
I also thought of an infinite loop, but it's not the case: because internally, foreach iterates on a copy of the array
Geoffray is correct. This is not a never ending loop. Foreach uses a copy as he says, a for loop and count() would be a never ending loop. @u_mulder
0

Direct Approach:

$array = [
    ["a" => "a", "b" => "aa", "number" => 3, "d" => 1],
    ["a" => "b", "b" => "bb", "number" => 1, "d" => 1],
    ["a" => "c", "b" => "cc", "number" => 3, "d" => 1],
];

foreach($array as $key => $value)
{
    if($value['number'] > 1) {
        array_unshift($array , $value, $value);
    }
}

echo "<pre>";
print_r($array);
  • take an array
  • check sub-array["value"] in conditions for true
  • append data at the beginning of the array( use array_push instead of array_unshift to insert at the end of the array)
  • this prevents pointer to the array unaffected until the loop ends
  • op did not mention any specific restrictions.

note:

check onto optimization.

  • EDIT - N+1 times Repeat: + Speed:
$output = [];
$times = 2; # set how many times you want to repeat it,

array_map(function($subArray) use(&$output, $times) {
    if($subArray['number']>1) {
        $output = array_merge($output, array_fill(0, $times, $subArray));
    } else {
        array_push($output, $subArray);
    }
}, $array);

PS: second approach maintains order for repeating values same value can benefit in better examination on it.

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4 Comments

"this prevents pointer to the array unaffected until the loop ends" - pointer is not disturbed unless you want to
I guess this also solves my problem. But the order of the elements is a bit strange. I get 2 "a" => "c" in the start of the array, and 1 at the end.
@johnohod let me check ps: you can have second one working well and Fine I have tested and is good in terms on speed.
@johnohod I did check that, as well I have mentioned in points, either you can use array_unshift or array_push.

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