Convert textarea to array and indented text to nested-arrays in PHP - php

Question

I am wanting to take text input from a Form Textarea POST in PHP and iterate over each line of text and create a PHP array with the text.
The catch is I want to take lines of text that are indented with 4 spaces before them and make those lines be a sub nested array under the above array item.
I am not sure how to do this at the moment so would appreciate any ideas on it.
// basic demo to show each line of textarea post
$text = $_POST['textarea'];
foreach(explode("\n", $text) as $line) {
echo $line;
echo '<br>';
}
UPDATE
An idea so far something along the lines of this as a start maybe....
$text = $_POST['textarea'];
$in_nested_array = false;
$array = array();
foreach(explode("\n", $text) as $line) {
if($line is 4 spaces){
$in_nested_array = true;
$array[''][$line];
}else{
//if in nested array and new line is not nested, add to root array
if($in_nested_array){
}else{
$in_nested_array = false;
$array[] = $line;
}
}
}

Answer 1

Just a first try:
$str = <<<EOD
bar
baz
meh
lol
tuuut
moo
EOD;
function parse($lines, $depth = 0, $cur = 0)
{
$retVal = array();
for ($i = $cur; $i < count($lines); $i++)
{
$line = $lines[$i];
$lDepth = strlen($line) - strlen(ltrim($line, " "));
if ($lDepth == $depth)
{
$retVal[] = array("line" => ltrim($line, " "));
} elseif ($lDepth == $depth + 4) {
$children = parse($lines, $depth + 4, $i);
$retVal[count($retVal) - 1]["children"] = $children;
$i += count($children);
}
}
return $retVal;
}
$lines = explode("\n", $str);
echo "<pre>";
print_r(parse($lines));
Output:
Array
(
[0] => Array
(
[line] => bar
[children] => Array
(
[0] => Array
(
[line] => baz
[children] => Array
(
[0] => Array
(
[line] => meh
)
[1] => Array
(
[line] => lol
[children] => Array
(
[0] => Array
(
[line] => tuuut
)
)
)
)
)
)
)
[1] => Array
(
[line] => moo
)
)

Answer 2

To seperate by 4 spaces:
$txt = preg_split('/ +/', $text);