PHP - Starting A Project, Need Some Direction Please

<?php
class steam {
    public $api = STEAM_API;
    public $returnUrl = URL;
    public $user = array();
    
    function __construct() {
        $this->setUserInfo();
    }
    
    function isLoggedin() {
        if(isset($_SESSION['steam'])) {
            return true;
        }
        return false;
    }
    
    function showLogoutButton() {
        echo "<br /><a href=\"logout.php\">Logout</a>"; //logout button
    }
    
    function steamlogin()
    {
        require_once(INCLUDES.'/openid.php');
        try {
            // Change 'localhost' to your domain name.
            $openid = new LightOpenID($this->returnUrl);
            //dump($openid);
            if(!$openid->mode) {
                if(isset($_GET['login'])) {
                    $openid->identity = 'http://steamcommunity.com/openid';
                    header('Location: ' . $openid->authUrl());
                }
                echo "<a href=\"?login\"><img src=\"http://steamcommunity-a.akamaihd.net/public/images/signinthroughsteam/sits_small.png\"></a>";
            } elseif($openid->mode == 'cancel') {
                echo 'User has canceled authentication!';
            } else {
                if($openid->validate()) {
                        $id = $openid->identity;
                        $ptn = "/^http:\/\/steamcommunity\.com\/openid\/id\/(7[0-9]{15,25}+)$/";
                        preg_match($ptn, $id, $matches);
                        $_SESSION['loginid'] = $matches[1];
                        //die('Here');
                        header('Location: index.php');
                        exit;
                } else {
                        echo "User is not logged in.\n";
                }
                //die('here we are');
            }
        } catch(ErrorException $e) {
            echo $e->getMessage();
        }
    }
    
    function doLogout() {
        if(isset($_POST['steamid'])) {
            unset($_POST['steamid']);
        }
        header('Location: index.php');
        exit;
    }	  
		
    function setUserInfo() {
        global $DB;
        
        if($this->isLoggedin()) {
        
            // Grab the info from the session
            $userData = $DB->getUserById($_SESSION['steam']);
            if(isset($userData['steamid'])) {
                $this->user = $userData;
            } else {
                unset($_SESSION['steam']);
                die('Could not get user');
            }
        
        } elseif(isset($_SESSION['loginid'])) {
            
        $url = 'http://api.steampowered.com/ISteamUser/GetPlayerSummaries/v0002/?key='.$this->api.'&steamids='.$_SESSION['loginid'];
        $ch = curl_init();
        curl_setopt( $ch, CURLOPT_URL, $url);
        curl_setopt( $ch, CURLOPT_RETURNTRANSFER, true);
        $content = curl_exec($ch);
        curl_close($ch);
        $content = json_decode($content, true);

        $_SESSION['steam'] = $_SESSION['loginid'];

        // Set the database values
        $values = array(
            'steamid' => $content['response']['players'][0]['steamid'],
            'communityvisibilitystate' => $content['response']['players'][0]['communityvisibilitystate'],
            'profilestate' => $content['response']['players'][0]['profilestate'],
            'personaname' => $content['response']['players'][0]['personaname'],
            'lastlogoff' => isset($content['response']['players'][0]['lastlogoff']) ? $content['response']['players'][0]['lastlogoff'] : '',
            'profileurl' => $content['response']['players'][0]['profileurl'],
            'avatar' => $content['response']['players'][0]['avatar'],
            'avatarmedium' => $content['response']['players'][0]['avatarmedium'],
            'avatarfull' => $content['response']['players'][0]['avatarfull'],
            'personastate' => $content['response']['players'][0]['personastate'],
            'timecreated' => $content['response']['players'][0]['timecreated'],       
            'onlineoffline' => $this->user['personastate'] == 1 ? 'Online' : 'Offline',
            'status' => $this->getOnlineStatus()
        );
        if($values['lastlogoff'] == '') {
            $values['lastlogoff'] = 'NA';
        } else {
            $values['lastlogoff'] = date("m/d/Y", $values['lastlogoff']);
        }      

        // Are updating the user info or adding them?
        $userExists = $DB->getUserById($_SESSION['steam']);
        if(isset($userExists['steamid'])) {
            // We have this user, lets update their info
            $DB->update('users', $values, array('steamid' => $_SESSION['steam']));
        } else {
            // New user, lets insert them
            $id = $DB->insert('users', $values);
        }


        unset($_SESSION['loginid']);
        $this->setUserInfo();
    }
}   
function getOnlineStatus($values) {

        switch($this->user['onlineoffline']) {

            case '0':

            default:

                $state = 'Offline';

            break;

            case '1':

                $state = 'Online';

            break;

            case '2':

                $state = 'Busy';

            break;

            case '3':

                $state = 'Away';

            break;

            case '4':

                $state = 'Snooze';

            break;

            case '5':

                $state = 'Looking to trade';

            break;

            case '6':

                $state = 'Looking to play';

            break;

        }

        return $state;

    }
?>

	echo "<br /><strong>Online:</strong> " . $steam->user['onlineoffline'] . " ";

<?php

  function getUploadedFiles($directory){
    $folder = opendir($directory);
    while ($file = readdir($folder)) {
    if($file !== '.' && $file !== '..')
    {
        $filename = $directory.''.$file;
        $file_array[] = array('filename' => $file);
    }
}
return $file_array;
  }

$music = getUploadedFiles('../Music/EDM');

foreach($music as $value)
{
	echo '<div class="well well-sm">';
	echo '<li class="list-group-item list-group-item-success"><div class="alert alert-success" role="alert"><a href="../Music/EDM/'.$value['filename'].'"title="Play .$value" class="sm2_button"></a> '.$value['filename'].'</div></li>';
	echo '<p><a href="../Music/EDM/'.$value['filename'].'"><button type="button" class="btn btn-sm btn-primary"><span class="glyphicon glyphicon-headphones"> </span>&nbsp; Listen</button></a>&nbsp;';
	echo '<a href="../Music/EDM/'.$value['filename'].'" download><button type="button" class="btn btn-sm btn-success"><span class="glyphicon glyphicon-cloud-download"></span>&nbsp; Download</button></p></br></a></p>';
	echo '<p><a class="btn btn-default" href="#" role="button">View details &raquo;</a></p>';
	echo '</div>';
	}

  ?>

Why do I get the following results (specifically the second example)?  I thought it would be documented under https://www.php.net/manual/en/language.types.string.php, however, the word "ampersand" doesn't appear.  Also, looked at logical operators, but found nothing.  Thanks

function test(string $string){
    printf('%s %s %s 0'.PHP_EOL, gettype($string), $string, $string==0?'==':'!=');
}

test('123');
test('@123');
test('1@23');
test('123@');

string 123 != 0
string @123 == 0
string 1@23 != 0
string 123@ != 0