php - Proper implementation of object parameters -

i want make sure i'm doing correctly. i'm little confused between $this->parameter, $parameter , public $parameter

here's example of i'm doing. want that's declared public able accessed $instance->parameter method. mean dot accessing work? being redundant?

class email {     public $textbody;     public $attachments;     public $subject;     public $emailfolder;      function __construct($header) {         $this->head = $header;         $this->attachments = [];         preg_match('/(?<=subject: ).*/', $this->head, $match);         $this->subject = $match[0];         if ($this->subject) {             $this->subject = "(no subject)";         }         preg_match('/(?<=from: ).*/', $this->head, $match);         $this->fromvar = $match[0];         preg_match('/(?<=to: ).*/', $this->head, $match);         $this->tovar = $match[0];         preg_match('/((?<=date: )\w+,\s\w+\s\w+\s\w+)|((?<=date: )\w+\s\w+\s\w+)/', $this->head, $match);         $this->date = $match[0];         $this->date = str_replace(',', '', $this->date);         $this->textbody = "";     }      function generateparsedemailfile($textfile) {         if (!(file_exists("/emails"))) {             mkdir("/emails");         }          $this->emailfolder =           $filepath = "/emails/".$this->subject.$this->date;         while (file_exists($filepath)) {             $filepath = $filepath.".1";         }              # ......code continues     } } 

no, . concatenating strings. public variables (as functions) accessible directly "outside" using -> operator, while protected , private variables (and functions) need getter , setter functions accessed. example this:

class myclass {     public $variablea;     protected $variableb;      public function setb($varb) {         $this->variableb = $varb;     }      public function getb() {         return $this->variableb;     } }  $object = new myclass();  $object->variablea = "new content"; // works $object->variableb = "new content"; // generates error $object->setb("new content");       // works