AwakenedYes

Trying to populate collection only as needed using callback function I am going through WROX Professional PHP5 Chapter 5 - Collections. I am trying to populate a collection from a DB (MSSQL) only as members are called, rather than populate everything, using callback functions as detailed in the book. I just can't get the result as expected, which is: "Bob Smith is currently enrolled in CS101". Hopefully the code will explain: //factoryTest.php <?php require_once 'class.Collection.php'; require_once 'class.CourseCollection.php'; require_once 'class.Course.php'; require_once 'class.Student.php'; require_once 'class.StudentFactory.php'; $studentID = 1; try { $objStudent = StudentFactory::getStudent($studentID); $objStudent2 = StudentFactory::getCoursesForStudent($studentID, $col); } catch (Exception $e) { die("Student #$studentID doesn't exist in the database!"); } print $objStudent . ($objStudent->courses->exists("CS101") ? ' is ' : ' is not '). 'currently enrolled in CS101'; //displays: "Bob Smith is enrolled in CS101" ?> //class.StudentFactory.php <?php class StudentFactory { public static function getStudent($id) { $serverName = ""; $connectionInfo = array("Database"=>"Registra"); $con = sqlsrv_connect($serverName, $connectionInfo) or die("Failure connecting to database!"); $sql = "SELECT * FROM \"student\" WHERE \"studentid\" = $id"; $result = sqlsrv_query($con, $sql); if ($result === false) { throw new Exception("Student $id does not exit."); } else { $row = sqlsrv_fetch_array($result, SQLSRV_FETCH_ASSOC); return new Student($row['studentid'], $row['name']); } } public static function getCoursesForStudent($id, $col) { $serverName = ""; $connectionInfo = array("Database"=>"Registra"); $con = sqlsrv_connect($serverName, $connectionInfo) or die("Failure connecting to database!"); $sql = "SELECT \"course\".\"courseid\", \"course\".\"coursecode\", \"course\".\"name\" FROM \"course\" INNER JOIN \"studentcourse\" ON \"course\".\"courseid\" = \"studentcourse\".\"courseid\" INNER JOIN \"student\" ON \"studentcourse\".\"studentid\" = \"student\".\"studentid\" WHERE \"course\".\"courseid\" = \"studentcourse\".\"courseid\" AND \"studentcourse\".\"studentid\" = $id"; $res = sqlsrv_query($con, $sql); if (sqlsrv_has_rows($res)) { $rowCount = sqlsrv_num_rows($res); while ($row = sqlsrv_fetch_array($res, SQLSRV_FETCH_ASSOC)) { $objCourse = new Course($row['courseid'], $row['coursecode'], $row['name']); $col->addItem($objCourse, $objCourse->getCourseCode()); // echo $row['courseid']." ".$row['coursecode']." ".$row['name']; } return $col; } } } ?> //class.Student.php <?php class Student { private $_id; private $_name; public $courses; public function __construct($id, $name) { $this->_id = $id; $this->_name = $name; $this->courses = new CourseCollection(); $this->courses->setLoadCallback('_loadCourses', $this); } public function getName() { return $this->_name; } public function getID() { return $this->_id; } public function _loadCourses(CourseCollection $col) { $courses = StudentFactory::getCoursesForStudent($this->_id, $col); } public function __toString() { return $this->_name; } } ?> //class.CourseCollection.php <?php class CourseCollection extends Collection { public function addItem(Course $obj, $key = null) { parent::addItem($obj, $key); } } ?> //class.Course.php <?php class Course { private $_id; private $_courseCode; private $_name; public function __construct($id, $courseCode, $name) { $this->_id = $id; $this->_courseCode; $this->_name; } public function getName() { return $this->_name; } public function getID() { return $this->_id; } public function getCourseCode() { return $this->_courseCode; } public function __toString() { return $this->_name; } } ?> //class.Collection.php <?php class Collection { private $_members = array(); // Collection members. private $_onload; // Holder for callback function private $_isLoaded = false; // Flag that indicates whether the // has been invoked. public function addItem($obj, $key = null) { $this->_checkCallback(); if ($key) { if (isset($this->_members[$key])) { throw new KeyInUseException("Key \"$key\" already in use!"); } else { $this->_members[$key] = $obj; } } else { $this->_members[] = $obj; } } public function removeItem($key) { $this->_checkCallback(); if (isset($this->_members[$key])) { unset($this->_members[$key]); } else { throw new KeyInvalidException("Invalid key \"$key\"!"); } } public function getItem($key) { $this->_checkCallback(); if (isset($this->_members[$key])) { return $this->_members[$key]; } else { throw new KeyInvalidException("Invalid key \"$key\"!"); } } public function length() { $this->_checkCallback(); return sizeof($this->_members); } public function keys() { $this->_checkCallback(); return array_keys($this->_members); } public function exists($key) { $this->_checkCallback(); return (isset($this->_members[$key])); } /** * Use this method to define a function to be invoked prior to accessing the * collection. The function should take a collection as its sole parameter. */ public function setLoadCallback($functionName, $objOrClass = null) { if ($objOrClass) { $callback = array($objOrClass, $functionName); } else { $callback = $functionName; } // Make sure the function/method is valid. if (! is_callable($callback, false, $callableName)) { throw new Exception("$callableName is not callable as a " . "parameter to onload"); return false; } $this->_onload = $callback; } /** * Check to see if a callback has been defined and if so, * whether or not it has already been called. If not, * invoke the callback function. */ private function _checkCallback() { if (isset($this->_onload) && ! $this->_isLoaded) { $this->_isLoaded = true; call_user_func($this->_onload, $this); } } } class KeyInvalidException extends Exception {} class KeyInUseException extends Exception {} ?> I always get "Bob Smith is not currently enrolled in CS101". Even in a foreach loop: foreach ($objStudent->courses as $objCourse) { print $objCourse->getCourseCode." - ".$objCourse->getName" } I don't get anything. What am I doing wrong? What am I missing? Is it going out of scope? The DB is connecting and returning correctly! Hope you can help - cheers

Hi Currently going through WROX Professional PHP5. Struggling to understand Chapter 5, which I'll post on another forum. Cheers