PHP $this variable

Question

I am reading some PHP code that I could not understand:

class foo {   function select($p1, $dbh=null) {     if ( is_null($dbh) )         $dbh = $this->dbh ;      return;    }    function get() {     return $this->dbh;    } } 

I can't find $this->dbh ($dbh) declaration from the class. My questions are:

• What is the value of $this->dbh ?

• Is it a local variable for function select()?

• Does $this belong class foo's data member? Why is there no declaration for $dbh in this class?

Answer 1

PHP is not strict for declaration. $this->dbh is a class member. I did the following code to understand the concept:

class foo {   function foo(){      $this->dbh = "initial value";   }   function select($p1, $dbh=null) {     if ( is_null($dbh) )         $dbh = $this->dbh ;      return;   }   function get() {      return $this->dbh;   }  } 

It is same as:

class foo {   var $dbh = "initial value";     function select($p1, $dbh=null) {     if ( is_null($dbh) )        $dbh = $this->dbh ;      return;    }    function get() {      return $this->dbh;    }  }