Assign values to an array inside a function

You're not capturing or returning the data:

function make_another_array(array $array) {
  foreach ($array as $key=>$value) {
    $another_array[$key] = $value;
  }

  return $another_array; // return here
}

$array = array(5 => 1, 12 => 2);
$another_array = make_another_array($array); // capture the returned value
print_r($another_array);

Secondly, you might just want to use this instead:

$another_array = array_values($array);

As by comment below, there is the pass by reference method:

function update_array(array &$array) {
  $array[3] = 12;
}
update_array($array);
print_r($array);

And finally, the not preferred method..

function update_array(array $a) {
  global $another_array;

  foreach($a as $key => $value){
    $another_array[$key] => $value;
  }
}

// or just array_merge
// $array = array_merge($array, $another_array);

You have to return the another_array inside the function: The variables declared inside a function are local-only, and the variables declared outside aren't accessible.

$array = array(5 => 1, 12 => 2);
$another_array = make_another_array($array);
print_r($another_array);

function make_another_array(array $array) {

    $another_array = array();
    foreach ($array as $key=>$value) {
       $another_array[$key] = $value;

    }
    return $another_array;
}

alternatively, you could also pass another array by reference:

$another_array = array();

$array = array(5 => 1, 12 => 2);
make_another_array($array, $another_array);
print_r($another_array);

function make_another_array(array $array, &$another_array) {

    foreach ($array as $key=>$value) {
       $another_array[$key] = $value;

    }
}

or, you could set them inside the function using the global keyword (but I'd recommend using the other two solutions):

$another_array = array();
$array = array(5 => 1, 12 => 2);
make_another_array($array);
print_r($another_array);

function make_another_array(array $array) {

    global $another_array;
    foreach ($array as $key=>$value) {
       $another_array[$key] = $value;

    }
}

and finally you could use the superglobal $GLOBALS, which is accessible in all scopes. (which is pretty the same as the sollution above)

$another_array = array();
$array = array(5 => 1, 12 => 2);
make_another_array($array);
print_r($another_array);

function make_another_array(array $array) {

    foreach ($array as $key=>$value) {
        $GLOBALS['another_array'][$key] = $value;

    }
}

You can pass it by reference like the following:

<?php
$another_array = array();
$array = array(5 => 1, 12 => 2);
function make_another_array($array, &$another_array) {

    foreach ($array as $key=>$value) {
       $another_array[$key] = $value;

    }
    return $another_array;
}
make_another_array($array, $another_array);
print_r($another_array);

http://ideone.com/mAAeTp

make sure there is a reference to $another_array as global to point to the one outside of function, otherwise it is local only.

global $another_array; // put this at the beginning of the make_another_array( function.

$another_array = array();
$array = array(5 => 1, 12 => 2); 
make_another_array($array); 
print_r($another_array); 

function make_another_array(array $array) 
{ 
    global $another_array;

    foreach ($array as $key=>$value){

        $another_array[$key] = $value; 

    }


}