Convert a flat associative array into an array of associative arrays with predetermined keys

foreach ($original_array as $key=>$value){
    $new_arrays[] = array('id'=>$key,'name'=>$value);
}

print_r($new_arrays);

You can do so:

$output_arr = array();
foreach($input_arr as $key => $value)
  $output_arr[] = array('id' => $key, 'name' => $value);

And then you can use $output_arr as converted array or assign its contents to $input_arr:

$input_arr = &$output_arr;

$input is your first array, $output will hold the resulting array

$output = array();
foreach ($input as $id => $name)
{
  $output[] = array('id'=>$id, 'name'=>$name);
}

Here are some more working solutions that endeavour to craft concise code.

Functional programming with parameter-derived associative keys Demo

var_export(
    array_map(
        fn(int $id, string $name) => get_defined_vars(),
        array_keys($array),
        $array
    )
);

Classic loop with associative keys born from foreach loop variable names Demo

$result = [];
foreach ($array as $id => $name) {
    $result[] = compact(['id', 'name']);
}
var_export($result);