如何解决compact（）函数中未定义的变量错误？

Question

I want to send email with some information. That's why I use compact() function within view() function. But I got an error 'undefined variable':

public $message_to_send="";
public $first_name_to_send="";

public function __construct($first_name,$message) {
    $this->message_to_send=$message;
    $this->first_name_to_send=$first_name;
}

public function build(){
    return $this->view('email/contactmessageemail',compact('message_to_send','first_name_to_send'));
}

The error message is:

compact(): Undefined variable: message_to_send

Answer 1

try to edit it to

view('email.contactmessageemail',[
   'message_to_send' => $this->message_to_send,
   'first_name_to_send' => $this->first_name_to_send
]);

compact didn't work in your case because the variables that you want to pass in is not locally defined in the method scope it is declared as a public property

Answer 2

This was a breaking changed introduced in PHP 7.3 with compact() . Previously, you could send through undefined variables with compact() , but now it flags as an error.

compact() is still a fantastic method - but you will need to define the variables within the method that you are using it. To keep code clean and readable, I suggest you define the variables and then pass using compact() as you had originally intended.

So you can fix using the original code like this:

public function build(){
    $message_to_send = $this->message_to_send;
    $first_name_to_send = $this->first_name_to_send;
    return view('email.contactmessageemail',compact('message_to_send','first_name_to_send'));
}

Note I removed $this from the view call.

You can also always pass the variables right into the build() method - which is sort of the norm - then you don't have to define within the method.