Detecting a cycle in an array PHP - php

Question

I'm running a simple script which puts an integer through the formula of the Collatz conjecture and adds the output of each step into an array.
I want to use a function to detect if there's a cycle in the array, using Floyd's algorithm. And though I feel like I'm not doing a bad job, I don't seem to get it right. At this moment I'm getting the error Trying to get property 'next' of non-object in C:\xampp\htdocs\educom\week3\functions.php on line 12
See my code below. Any feedback is greatly appreciated!
include("functions.php");
$n = $_POST['number'];
$step = 0;
$reeks1 = array();
$cycle = 0;
echo "Your entry is: ". $n ."<br><br>";
while($n!==1 && $cycle==0){
$cycle = detect_cycle(array($reeks1));
if($n % 2 == 0){
$n = $n / 2;
array_push($reeks1, "$n");
$step++;
echo $step .": ". $n ."<br>";
}else{
$n = ($n * 3) + 1;
array_push($reeks1, "$n");
$step++;
echo $step .": ". $n ."<br>";
}
}
functions.php:
function detect_cycle($node){
if ($node==NULL){
return FALSE;
}
$turtle = $node;
$rabbit = $node->next;
while($rabbit != NULL){
if($rabbit === $turtle){
return TRUE;
}elseif($rabbit->next == NULL){
return FALSE;
}else{
$turtle = $turtle->next;
$rabbit = $rabbit->next->next;
}
}
return FALSE;
}

Answer 1

Check this out. IMPORTANT I don't know is this according to your theory. but it won't give you errors if you use like this.
function detect_cycle($node){
if ($node==NULL){
return FALSE;
}
$turtle = $node;
$rabbit = $node[0];
while($rabbit != NULL){
if($rabbit === $turtle){
return TRUE;
}elseif($rabbit[0] == NULL){
return FALSE;
}else{
$turtle = $turtle[0]; // use the number of the element key starting from 0
$rabbit = $rabbit[0][1];
}
}
return FALSE;
}