array_change_key_case

Unicode example;

<?php
function array_change_key_case_unicode($arr, $c = CASE_LOWER) {
    $c = ($c == CASE_LOWER) ? MB_CASE_LOWER : MB_CASE_UPPER;
    foreach ($arr as $k => $v) {
        $ret[mb_convert_case($k, $c, "UTF-8")] = $v;
    }
    return $ret;
}

$arr = array("FirSt" => 1, "yağ" => "Oil", "şekER" => "sugar");
print_r(array_change_key_case($arr, CASE_UPPER));
print_r(array_change_key_case_unicode($arr, CASE_UPPER));
?>

Array
(
    [FIRST] => 1
    [YAğ] => Oil
    [şEKER] => sugar
)
Array
(
    [FIRST] => 1
    [YAĞ] => Oil
    [ŞEKER] => sugar
)

Here is the most compact way to lower case keys in a multidimensional array

function array_change_key_case_recursive($arr)
{
    return array_map(function($item){
        if(is_array($item))
            $item = array_change_key_case_recursive($item);
        return $item;
    },array_change_key_case($arr));
}

I improve the array_change_key_case_recursive function ,let it can lowercase or uppercase keys

function array_change_key_case_recursive($arr, $case = CASE_LOWER)
{
    return array_map(function($item) use($case) {
        if(is_array($item))
            $item = array_change_key_case_recursive($item, $case);
        return $item;
    },array_change_key_case($arr, $case));
}

Improved multidimensional unicode func (after qeremy):
<?php
function array_change_key_case_unicode_recurs($arr, $c = CASE_LOWER) {
    foreach ($arr as $k => $v) {
        $ret[mb_convert_case($k, (($c === CASE_LOWER) ? MB_CASE_LOWER : MB_CASE_UPPER), "UTF-8")] = (is_array($v) ? array_change_key_case_unicode_recurs($v, $c) : $v );
    }
    return $ret;
}

$arr = array("FirSt" => 1, "ZażóŁć gęŚlą jaŹń" => array("yağ" => "Oil", "şekER" => "sugar") );
print_r(array_change_key_case($arr, CASE_UPPER));
print_r(array_change_key_case_unicode_recurs($arr, CASE_UPPER));
?>

Array
(
    [FIRST] => 1
    [ZAżóŁć GęŚLą JAŹń] => Array
        (
            [yağ] => Oil
            [şekER] => sugar
        )
)
Array
(
    [FIRST] => 1
    [ZAŻÓŁĆ GĘŚLĄ JAŹŃ] => Array
        (
            [YAĞ] => Oil
            [ŞEKER] => sugar
        )
)

multibyte and multi-dimensional-array support, have fun!

<?php
    define('ARRAY_KEY_FC_LOWERCASE', 25); //FOO => fOO
    define('ARRAY_KEY_FC_UPPERCASE', 20); //foo => Foo
    define('ARRAY_KEY_UPPERCASE', 15); //foo => FOO
    define('ARRAY_KEY_LOWERCASE', 10); //FOO => foo
    define('ARRAY_KEY_USE_MULTIBYTE', true); //use mutlibyte functions
    
    /**
    * change the case of array-keys
    *
    * use: array_change_key_case_ext(array('foo' => 1, 'bar' => 2), ARRAY_KEY_UPPERCASE);
    * result: array('FOO' => 1, 'BAR' => 2)
    *
    * @param    array
    * @param    int
    * @return     array
    */
    function array_change_key_case_ext(array $array, $case = 10, $useMB = false, $mbEnc = 'UTF-8') {
        $newArray = array();
        
        //for more speed define the runtime created functions in the global namespace
        
        //get function
        if($useMB === false) {
            $function = 'strToUpper'; //default
            switch($case) {
                //first-char-to-lowercase
                case 25:
                    //maybee lcfirst is not callable
                    if(!function_exists('lcfirst')) 
                        $function = create_function('$input', '
                            return strToLower($input[0]) . substr($input, 1, (strLen($input) - 1));
                        ');
                    else $function = 'lcfirst';
                    break;
                
                //first-char-to-uppercase                
                case 20:
                    $function = 'ucfirst';
                    break;
                
                //lowercase
                case 10:
                    $function = 'strToLower';
            }
        } else {
            //create functions for multibyte support
            switch($case) {
                //first-char-to-lowercase
                case 25:
                    $function = create_function('$input', '
                        return mb_strToLower(mb_substr($input, 0, 1, \'' . $mbEnc . '\')) . 
                            mb_substr($input, 1, (mb_strlen($input, \'' . $mbEnc . '\') - 1), \'' . $mbEnc . '\');
                    ');
                    
                    break;
                
                //first-char-to-uppercase
                case 20:
                    $function = create_function('$input', '
                        return mb_strToUpper(mb_substr($input, 0, 1, \'' . $mbEnc . '\')) . 
                            mb_substr($input, 1, (mb_strlen($input, \'' . $mbEnc . '\') - 1), \'' . $mbEnc . '\');
                    ');
                    
                    break;
                
                //uppercase
                case 15:
                    $function = create_function('$input', '
                        return mb_strToUpper($input, \'' . $mbEnc . '\');
                    ');
                    break;
                
                //lowercase
                default: //case 10:
                    $function = create_function('$input', '
                        return mb_strToLower($input, \'' . $mbEnc . '\');
                    ');
            }
        }
        
        //loop array
        foreach($array as $key => $value) {
            if(is_array($value)) //$value is an array, handle keys too
                $newArray[$function($key)] = array_change_key_case_ex($value, $case, $useMB);
            elseif(is_string($key))
                $newArray[$function($key)] = $value;
            else $newArray[$key] = $value; //$key is not a string
        } //end loop
        
        return $newArray;
    }
?>

<?php
/**
 * Convert keys in an array.
 * 
 * @param array $array Source data
 * @param callable $callback Function name (strtolower, strtoupper, ucfirst, lcfirst, ucwords)
 * @return array
 */
function array_convert_key_case(array $array, callable $callback = 'strtolower')
{
    return array_combine(
        array_map($callback, array_keys($array)),
        array_values($array)
    );
}
?>

Array of partitions with always the same number of sub-array indexes.

<?php

function partitionFixedSubArray($array, $length, $empty_space)
{   
    $result = [];

    if ( sizeof($array) ) {

        $result = array_chunk($array, $length);
        $last_array_count = sizeof(end($result));

        if ($last_array_count < $length) {

            for ($i = $last_array_count; $i < $length; $i++) {
                array_push($result[key($result)], $empty_space);
            }
        }
    }

    return $result;
}

$employees = [
    "Paidi",
    "Paijo",
    "Darno",
    "Kusnan",
    "Mukidi",
    "Sarno",
    "Nurdin",
    "Parmen",
    "Sukinah",
    "Sartini",
    "Sukijan",
    "Yono",
    "Supoyo"
];

echo "<pre>";
print_r(partitionFixedSubArray($employees, 5, "empty space"));
echo "</pre>";

?>

Output:
Array
(
    [0] => Array
        (
            [0] => Paidi
            [1] => Paijo
            [2] => Darno
            [3] => Kusnan
            [4] => Mukidi
        )

    [1] => Array
        (
            [0] => Sarno
            [1] => Nurdin
            [2] => Parmen
            [3] => Sukinah
            [4] => Sartini
        )

    [2] => Array
        (
            [0] => Sukijan
            [1] => Yono
            [2] => Supoyo
            [3] => empty space
            [4] => empty space
        )

)

Use this to capitalize first letter of all array keys:

<?php

function ucfirstKeys(&$data)
{
  foreach ($data as $key => $value)
  {
    // Convert key
    $newKey = ucfirst($key);

    // Change key if needed
    if ($newKey != $key)
    {
      unset($data[$key]);
      $data[$newKey] = $value;
    }

    // Handle nested arrays
    if (is_array($value))
    {
      ucfirstKeys($data[$key]);
    }
  }
}

$test = array('foo' => 'bar', 'moreFoo' => array('more' => 'foo'));
ucfirstKeys($test);
print_r($test);

?>

Result:
Array ( [MoreFoo] => Array ( [More] => foo ) [Foo] => bar )

I just changed the code a little bit so you havent got a code that repeats itself.

<?php

function array_change_key_case_secure($array = array(), $case = CASE_UPPER){
    $secure = array();
    $functionWrap = array(CASE_UPPER => 'strtoupper',
                            CASE_LOWER => 'strtolower');
                            
    foreach($array as $key => $val){
        if(isset($functionWrap[$key])){
            $key = $functionWrap[$case]($key);
            $secure[$key][] = $val;
        } else {
            die('Not a known Type');
        }
    }
    
    foreach($secure as $key => $val){
        if(count($secure[$key]) == 1){
            $secure[$key] = $val[0];
        }
    }
    
    return $secure;
}

$myArray = array('A' => 'Hello',
                    'B' => 'World',
                    'a' => 'how are you?');

print_r($myArray);
$myArray = array_change_key_case_secure($myArray);
print_r($myArray);

/*
Array
(
    [A] => Hello
    [B] => World
    [a] => how are you?
)
Array
(
    [A] => Array
        (
            [0] => Hello
            [1] => how are you?
        )

    [B] => World
)
*/

<?php
function array_change_value_case($input, $case = CASE_LOWER)
{
    $aRet = array();
    
    if (!is_array($input))
    {
        return $aRet;
    }
    
    foreach ($input as $key => $value)
    {
        if (is_array($value))
        {
            $aRet[$key] = array_change_value_case($value, $case);
            continue;
        }
        
        $aRet[$key] = ($case == CASE_UPPER ? strtoupper($value) : strtolower($value));
    }
    
    return $aRet;
}
?>

Below is a recursive version of this function.

<?php
    /**
     * A recursive array_change_key_case function.
     * @param array $input
     * @param integer $case
     */
    function array_change_key_case_recursive($input, $case = null){
        if(!is_array($input)){
            trigger_error("Invalid input array '{$array}'",E_USER_NOTICE); exit;
        }
        // CASE_UPPER|CASE_LOWER
        if(null === $case){
            $case = CASE_LOWER;
        }
        if(!in_array($case, array(CASE_UPPER, CASE_LOWER))){
            trigger_error("Case parameter '{$case}' is invalid.", E_USER_NOTICE); exit;
        }
        $input = array_change_key_case($input, $case);
        foreach($input as $key=>$array){
            if(is_array($array)){
                $input[$key] = array_change_key_case_recursive($array, $case);
            }
        }
        return $input;
    }
?>

//Array key case change recursively (Unicode):

<?php
function array_key_case($data,$case=FALSE)
{
    $ret=array();
    if ( is_array($data) )            
        foreach ($data as $idx => $val)                   
            $ret[$case ? mb_strtoupper($idx) : mb_strtolower($idx)]=array_key_case($val,$case);            
    else
        $ret=$data;
    return $ret;
}