Question: I need to restructure some array data then pass it as a json string to generate a Google line chart.

In the result array, I need to create rows of three elements.

1. the original element keys which are shared among all rows.
2. the values from the first row.
3. the values from the second row.

Input array:

```
[
    1 => [
        1 => 'c1',
        2 => 'c1',
        3 => 'c1',
        4 => 'c1',
        5 => 'c1'
    ],
    10 => [
        1 => 'c2',
        2 => 'c2',
        3 => 'c2',
        4 => 'c2',
        5 => 'c2'
    ]
]

```

Expected result is:

```
[[1,"c1","c2"],[2,"c1","c2"],[3,"c1","c2"],[4,"c1","c2"],[5,"c1","c2"]]

```

Answer: 
**Two nested loops** should do the trick in this case:

```
$input = /* your input array */;
$grouped = array();

foreach ($input as $elements) {
    foreach ($elements as $key => $element) {
        $grouped[$key][] = $element;
    }
}

```

This produces an array that looks like the following:

```
array(
    1 => array(c1, c2, ...),
    2 => array(c1, c2, ...),
    ...
);

```

This can the easily be converted to your desired output:

```
$output = "";
foreach ($grouped as $name => $values) {
    $output .= "['$name'";
    foreach ($values as $value)
        $output .= ", $value";
    $output .= "],\n";
}

```

Which will produce:

```
$output = "['1', c1, c2],\n['2', c1, c2]\n,...";

```
You merely need to include the keys from the first row in your [array transposition](https://stackoverflow.com/q/797251/2943403).

Also, it is crucial that you never manually generate json string by string concatenation (or any other manual method). The surest way to generate a valid json string is to call `json_encode()`.

Code: ([Demo](https://3v4l.org/kdgBX))

```
echo json_encode(
    array_map(
        null,
        array_keys(current($arr)),
        ...$arr
    )
);

```