PHP/Laravel disappearing variable - php

Question

I have some very strange behaviour in an app I am working on. In the example below there are 2 functions.
public function updatePhpVhostVersions(Request $r) {
$data = array(
'hostname' => $r['hostname'],
'username' => $r['username'],
'vhost' => $r['vhost'],
'php_version' => $r['php_version']
);
$result = Cpanel::setPhpVhostVersions($data)->data;
if($r->ajax()){
return Response::json($result);
}
return $result;
}
public function getInstalledPhpVersions(Request $r) {
$data = array(
'hostname' => $r['hostname'],
'username' => $r['username']
);
$result = Cpanel::getInstalledPhpVersions($data)->data;
if($r->ajax()){
return Response::json($result);
}
return $result;
}
The two functions contain Cpanel:: ... ($data)->data; this gets handeled by a __call method. In this method I use a function that prepares some vars, caching, etc. to simplify things I have combined some functions into one.
private function prepare($function, $arguments) {
// Dettirmine what will be used
$this->function = $function;
$nameSplit = preg_split('/(?=\p{Lu})/u', $function);
$this->class = 'App\\Phase\\Cpanel\\' . $this->folder($nameSplit) . '\\' . $this->file($nameSplit);
// Cache True/False
if(isset($this->arguments['cache'])) {
$this->cache = $this->arguments['cache'];
}
// Get the provided arguments
// these are used in the API post
if(isset($arguments[0]['hostname'], $arguments[0]['username'])) {
$arguments = $arguments[0];
}
$this->arguments = $arguments;
// Flush the cache when needed
if (!$this->cache || in_array($nameSplit[0], array('create', 'delete', 'add', 'install', 'set'))) {
try {
Cache::tags(['cpanel', $this->function . $arguments['username']])
->flush();
} catch (Exception $e) {
dd($arguments);
}
}
}
The prepare method is used every time the __call method gets used. In Cpanel::setPhpVhostVersion() the $arguments somehow get empty after the following if statement.
// Flush the cache when needed
if (!$this->cache || in_array($nameSplit[0], array('create', 'delete', 'add', 'install', 'set'))) {
try {
Cache::tags(['cpanel', $this->function . $arguments['username']])
->flush();
} catch (Exception $e) {
dd($e);
}
}
Before Cache::tags() the $arguments contains an array with some user information. But when Cache::tags()->flush() gets called it throws an exception that $arguments['username'] is empty. Now if I dd($arguments) after this, it returns an empty array. If I dd() before this the array still has the information. This only happens with Cpanel::setPhpVhostVersion() not with the 37 other possible Cpanel:: ... () what could be causing this?
EDIT
After some playing around with the code, I noticed that $arguments gets empty everytime after it gets used. It does not matter where, it just gets empty. (But only with setPhpVhostVersions)
Example
if(!isset($this->arguments['username'])) {
return Api::respondUnauthenticated('Account username is a required parameter');
}
Before the !isset() the $arguments['username'] exists, during and after the !isset() I get the exception:
ErrorException: Undefined index: username