need help in php class and object

i am getting error in following php code

<?
class sewatch {
public $sum=$this->add();
public function add()
{
return 5;
}

}
$o=new sewatch();
echo $o->sum;
?>

PHP:

Parse error: parse error in C:\wamp\www\mainclass.php on line 3

Code (markup):

 

i would believe it needs ;

here

 

What are you trying to do exactly? The problem you have is here;

public $sum=$this->add();

PHP:

Without understanding what you are trying to achieve, exactly, its hard to answer although this;

<?
class sewatch {

public $sum = null;

public function __construct()
{
$this->sum = $this->add();
}

public function add()
{
return 5;
}
}
$o=new sewatch();
echo $o->sum;
?>

PHP:

Will output "5" if that is all you need.

 

The 3rd line is not valid, see this documentation page from PHP.net

<?php
class SimpleClass
{
   // invalid property declarations:
   public $var1 = 'hello ' . 'world';
   public $var2 = <<<EOD
hello world
EOD;
   public $var3 = 1+2;
   public $var4 = self::myStaticMethod();
   public $var5 = $myVar;

   // valid property declarations:
   public $var6 = myConstant;
   public $var7 = array(true, false);

   // This is allowed only in PHP 5.3.0 and later.
   public $var8 = <<<'EOD'
hello world
EOD;
}
?>

PHP:

As suggested by lukeg32, you should declare the property then set it's value inside the constructor method __construct()