PHP-致命错误：不在对象上下文中时使用$ this

Question

I'm really sorry to be asking this question because I know it has been asked many times before (and I have read the threads) but I just can't puzzle this out.

I have a class:

class Fivehundredpx {
    private $_user;
    public $fivehundredpx;

    public function __construct(User $user){ 
        $this->_user = $user->data();
        $this->fivehundredpx = $user->data()->fivehundredpx;
    }

    public function fhpxEndpoint(){ //truncated - this function actually has a number of switch statements
        return $apistring = "https://api.500px.com/v1/photos?feature=user_favorites&username=". $this->fivehundredpx."&sort=rating&image_size=3&include_store=store_download&include_states=voted&consumer_key=I9CDYnaxrFxLTEvYxTmsDKZQlgStJG868GKb"; //this is the line that causes the error
    }

}

when fhpxEndpoint() is called I get the Fatal error: Using $this when not in object context message.

However if I add another method into the class:

public function userData(){
    print 'here is some text '. $this->fivehundredpx;
}

and call this from outside the class it prints out here is some text jinky32 as expected.

Any help much appreciated!

edit as per request: method is called via

$fivehundredpx = new Fivehundredpx;
$obj = $fivehundredpx->fhpxApiConnect($fivehundredpx->fhpxEndpoint());

fhpxApiConnect() is:

public function fhpxApiConnect($apiString){
    print $apiString;
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL,$apiString);
    curl_setopt($ch , CURLOPT_HEADER, 0);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1); 
etc etc

printing out $apiString as I do in fhpxApiConnect() shows that the url has been constructed correctly and the name jinky32 has been inserted correctly but i still get the fatal error

EDIT: OK, I've played around and found a way to get it to work. If I change the class variable to

public static $fivehundredpx;

and then set it

public function __construct(User $user){
    self::$fivehundredpx=$user->data()->fivehundredpx;
}

I can then access it in fhpxEndpoint() using self::$fivehundredpx rather than $this->fivehundredpx

Answer 1

Try this:

public function userData(){
    print 'here is some text '. Fivehundredpx::fivehundredpx();
}

or can try with:

public function userData(){
    $obj = new Fivehundredpx();
    print 'here is some text '. $obj->fivehundredpx();
}

Answer 2

Based on your comment, you can't access to a property of User like this:

$user->data()->fivehundredpx;

While method data of class User doesn't return your object. Add to method data:

return $this;

at the end.