Recursive PHP Function - php

Question

I am trying to solve this problem to learn logic formulations, but this one's really taken too much of my time already.
Rules are simple, No loops and no built in PHP functions (eg. print_r, is_array.. etc).
This is what I have come up with so far.
function displayArray(array $inputArray, $ctr = 0, $tempArray = array()) {
//check if array is equal to temparray
if($inputArray != $tempArray) {
// check if key is not empty and checks if they are not equal
if($inputArray[$ctr]) {
// set current $tempArray key equal to $inputArray's corresponding key
$tempArray[$ctr] = $inputArray[$ctr];
if($tempArray[$ctr] == $inputArray[$ctr]) {
echo $tempArray[$ctr];]
}
$ctr++;
displayArray($inputArray, $ctr);
}
}
}
This program outputs this:
blackgreen
The problem starts when it reaches the element that is an array
$array = array(
'black',
'green',
array(
'purple',
'orange'
)
);
displayArray($array);
Any tips?
This what the return value is supposed to be: blackgreenpurpleorange

Answer 1

This was fun. I decided to make it work with most data types while I was at it. Just don't throw it any objects or nulls and things should work.
No more # error suppression. Now returns the string instead of echoing it.
I realized too late that isset() is actually a language construct rather than a function, and went with a null termination strategy to determine the end of the arrays.
function concatinateRecursive($array, $i = 0) {
static $s = '';
static $depth = 0;
if ($i == 0) $depth++;
// We reached the end of this array.
if ($array === NULL) {
$depth--;
return true;
}
if ($array === array()) return false; // empty array
if ($array === '') return false; // empty string
if (
$array === (int)$array || // int
$array === (float)$array || // float
$array === true || // true
$array === false || // false
$array === "0" || // "0"
$array == "1" || // "1" "1.0" etc.
(float)$array > 1 || // > "1.0"
(int)$array !== 1 // string
)
{
$s .= "$array";
return false;
}
// Else we've got an array. Or at least something we can treat like one. I hope.
$array[] = NULL; // null terminate the array.
if (!concatinateRecursive($array[$i], 0, $s)) {
$depth--;
return concatinateRecursive($array, ++$i, $s);
}
if ($depth == 1) {
return $s;
}
}
$array = array(
'black',
'green',
array(
'purple',
'orange'
)
);
echo concatinateRecursive($array);
blackgreenpurpleorange
Live demo

Answer 2

What about this? You must check if it is array or not.
function display_array(&$array, $index=0) {
if (count($array)<=$index) return;
if (is_array($array[$index])) {
echo '[ ';
display_array($array[$index]);
echo '] ';
}
else
echo "'" . $array[$index] . "' ";
display_array($array, $index+1);
}
// Try:
// $a = ['black', 'green', ['purple', 'orange'], 'beer', ['purple', ['purple', 'orange']]];
// display_array($a);
// Output:
// 'black' 'green' [ 'purple' 'orange' ] 'beer' [ 'purple' [ 'purple' 'orange' ] ]

Answer 3

try this have to use some inbuilt function like isset and is_array but its a complete working recursive method without using loop.
function displayArray(array $inputArray, $ctr = 0) {
if(isset($inputArray[$ctr]))
{
if(is_array($inputArray[$ctr]))
{
return displayArray($inputArray[$ctr]);
}
else
{
echo $inputArray[$ctr];
}
}
else
{
return;
}
$ctr++;
displayArray($inputArray, $ctr);
}
$array = array(
'black',
'green',
array(
'purple',
'orange'
)
);
displayArray($array);
OUTPUT :
blackgreenpurpleorange
DEMO

Answer 4

complete answer
$myarray = array(
'black',
'green',
array(
'purple',
'orange'
)
);
function printAll($a) {
if (!is_array($a)) {
echo $a, ' ';
return;
}
foreach($a as $k => $value) {
if($k<10){
//printAll($k);
printAll($value);
}
}
}
printAll($myarray);