如何调用类方法？

Question

I have a problem with my code, when I try to use private function sqlConnection(){

I have this code:

<?php
require "transferDao/daoTransferProyectos.php";
class daoProyectos{
private function sqlConnection(){

        try {

            $servername = "localhost"; 
            $username = "root";
            $password = "123asd";
            $conn = new PDO("mysql:host=$servername;dbname=bd_actividades", $username, $password);
            $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);  

        }
        catch(PDOException $e)
        {
        echo "Connection failed: " . $e->getMessage();
        }
    }   
 public function resultSelect(){

            $aObjects=array();

            $db = sqlConnection();
            $stmt = $db->prepare("SELECT pro_id, pro_nombre FROM act_proyecto");
            $stmt->execute();
            $stmt->setFetchMode(PDO::FETCH_ASSOC);
            $result = $stmt->fetchAll();

            foreach ($result as $row) {
            $aTransfer = new daoTransferProyectos();
            $aTransfer->setId($row['pro_id']);
            $aTransfer->setNombreProyecto($row['pro_nombre']);
            $aObjects[]=$aTransfer;
            }
            return $aObjects;
    }
}
?>

And I have this error:

[Mon Jun 01 21:56:00.569136 2015] [:error] [pid 7015] [client 10.0.2.2:61625] PHP Fatal error: Call to undefined function sqlConnection() in /var/www/html/PROJECTS/dailytasks/dao/daoProyectos.php on line 28, referer: http://localhost:8080/formulario_web/formulario/formulario_lazos.html

How can I fix this error?

EDIT:

If I use:

$db = $this->sqlConnection();

Then I get a new error:

[Mon Jun 01 22:11:00.530604 2015] [:error] [pid 7015] [client 10.0.2.2:61957] PHP Fatal error: Call to a member function prepare() on a non-object in /var/www/html/PROJECTS/dailytasks/dao/daoProyectos.php on line 29, referer: http://localhost:8080/formulario_web/formulario/formulario_lazos.html

Answer 1

This:

$db = sqlConnection();

should be:

$db = $this->sqlConnection();
    //^^^^^^^ See here

In other words, you're trying to call a global function, which doesn't exist, instead of your object's method. e.g.

function foo() {
   echo 'global function foo';
}

class bar() {
   function foo() {
      echo 'method foo';
   }
   function bar() {
      foo();        // prints: global function foo
      $this->foo(); // prints: method foo
   }
}

and