语法中的未知错误[重复]

While working with an OOP script in PHP upon parsing I get a syntax error I know shouldn't be there. The syntax is perfect.

class Organism
 {
  private $ex = array(0=>"Hello",1=>"world!");
  public $ex2 = array_rand($ex,1);
 }

Gives me the error of

Parse error: syntax error, unexpected '(', expecting ',' or ';'

</div>

In PHP you must implement constructor and assign default values for your variables there.

private $ex = array(0=>"Hello",1=>"world!"); // Will work (not a function/not dynamic)

public $ex2 = array_rand($ex,1);  //A function call won't work

Solution:

class Organism
 {
    private $ex = array(0=>"Hello",1=>"world!");
    public $ex2 ;

    public function __construct(){
      $this->ex2 = array_rand($this->ex,1);
    }
 }