Php：学习OOP，静态方法与常规方法

Question

This is my first post in Stack Overflow so bear with me if I don't conform to any of the rules. I have been scripting in php for a while now but have never actually used any of its OOP side. I have been doing a training course on-line (not sure if i'm aloud to state which one because of copyright ?)

Either way during the course the programmer made a few static methods inside of one of his class, I decided i didn't want to make mine static. Here is the code he writ below. I did mine all the same just with different references to the variables in the code like $this->variable.

`<?php
// If it's going to need the database, then it's 
// probably smart to require it before we start.
require_once(LIB_PATH.DS.'database.php');

class Photograph extends DatabaseObject {

    protected static $table_name="photographs";
    protected static $db_fields=array('id', 'filename', 'type', 'size', 'caption');
    public $id;
    public $filename;
    public $type;
    public $size;
    public $caption;

    private $temp_path;
  protected $upload_dir="images";
  public $errors=array();

   protected $upload_errors = array(
        // http://www.php.net/manual/en/features.file-upload.errors.php
        UPLOAD_ERR_OK               => "No errors.",
        UPLOAD_ERR_INI_SIZE     => "Larger than upload_max_filesize.",
       UPLOAD_ERR_FORM_SIZE     => "Larger than form MAX_FILE_SIZE.",
       UPLOAD_ERR_PARTIAL       => "Partial upload.",
       UPLOAD_ERR_NO_FILE       => "No file.",
      UPLOAD_ERR_NO_TMP_DIR => "No temporary directory.",
      UPLOAD_ERR_CANT_WRITE => "Can't write to disk.",
      UPLOAD_ERR_EXTENSION  => "File upload stopped by extension."
    );

     // Pass in $_FILE(['uploaded_file']) as an argument
  public function attach_file($file) {
        // Perform error checking on the form parameters
        if(!$file || empty($file) || !is_array($file)) {
          // error: nothing uploaded or wrong argument usage
          $this->errors[] = "No file was uploaded.";
          return false;
         } elseif($file['error'] != 0) {
          // error: report what PHP says went wrong
          $this->errors[] = $this->upload_errors[$file['error']];
          return false;
        } else {
            // Set object attributes to the form parameters.
          $this->temp_path  = $file['tmp_name'];
          $this->filename   = basename($file['name']);
          $this->type       = $file['type'];
          $this->size       = $file['size'];
            // Don't worry about saving anything to the database yet.
             return true;

         }
    }

    public function save() {
        // A new record won't have an id yet.
        if(isset($this->id)) {
            // Really just to update the caption
            $this->update();
        } else {
            // Make sure there are no errors

            // Can't save if there are pre-existing errors
          if(!empty($this->errors)) { return false; }

            // Make sure the caption is not too long for the DB
          if(strlen($this->caption) > 255) {
                $this->errors[] = "The caption can only be 255 characters  long.";
                return false;
            }

          // Can't save without filename and temp location
          if(empty($this->filename) || empty($this->temp_path)) {
            $this->errors[] = "The file location was not available.";
            return false;
          }

            // Determine the target_path
          $target_path = SITE_ROOT .DS. 'public' .DS. $this->upload_dir .DS. $this->filename;

          // Make sure a file doesn't already exist in the target location
          if(file_exists($target_path)) {
            $this->errors[] = "The file {$this->filename} already exists.";
            return false;
          }

            // Attempt to move the file 
            if(move_uploaded_file($this->temp_path, $target_path)) {
            // Success
                 // Save a corresponding entry to the database
                if($this->create()) {
                    // We are done with temp_path, the file isn't there anymore
                     unset($this->temp_path);
                    return true;
                }
            } else {
                // File was not moved.
             $this->errors[] = "The file upload failed, possibly due to incorrect permissions on the upload folder.";
             return false;
            }
        }
    }

    public function destroy() {
        // First remove the database entry
        if($this->delete()) {
            // then remove the file
           // Note that even though the database entry is gone, this object 
            // is still around (which lets us use $this->image_path()).
              $target_path = SITE_ROOT.DS.'public'.DS.$this->image_path();
            return unlink($target_path) ? true : false;
        } else {
            // database delete failed
            return false;
        }
    }
     public function image_path() {
       return $this->upload_dir.DS.$this->filename;
    }

     public function size_as_text() {
        if($this->size < 1024) {
            return "{$this->size} bytes";
        } elseif($this->size < 1048576) {
            $size_kb = round($this->size/1024);
            return "{$size_kb} KB";
        } else {
            $size_mb = round($this->size/1048576, 1);
            return "{$size_mb} MB";
        }
    }


// Common Database Methods
public static function find_all() {
    return self::find_by_sql("SELECT * FROM ".self::$table_name);
  }

  public static function find_by_id($id=0) {
      global $database;
    $result_array = self::find_by_sql("SELECT * FROM ".self::$table_name."  WHERE id=".$database->escape_value($id)." LIMIT 1");
        return !empty($result_array) ? array_shift($result_array) : false;
  }

  public static function find_by_sql($sql="") {
     global $database;
    $result_set = $database->query($sql);
    $object_array = array();
    while ($row = $database->fetch_array($result_set)) {
       $object_array[] = self::instantiate($row);
    }
        return $object_array;
  }

    private static function instantiate($record) {
    // Could check that $record exists and is an array
$object = new self;
    // Simple, long-form approach:
    // $object->id              = $record['id'];
    // $object->username    = $record['username'];
    // $object->password    = $record['password'];
    // $object->first_name = $record['first_name'];
    // $object->last_name   = $record['last_name'];

    // More dynamic, short-form approach:
    foreach($record as $attribute=>$value){
      if($object->has_attribute($attribute)) {
        $object->$attribute = $value;
      }
    }
    return $object;
}

private function has_attribute($attribute) {
  // We don't care about the value, we just want to know if the key exists
  // Will return true or false
  return array_key_exists($attribute, $this->attributes());
}

protected function attributes() { 
    // return an array of attribute names and their values
  $attributes = array();
  foreach(self::$db_fields as $field) {
    if(property_exists($this, $field)) {
      $attributes[$field] = $this->$field;
    }
  }
  return $attributes;
}

protected function sanitized_attributes() {
  global $database;
  $clean_attributes = array();
  // sanitize the values before submitting
  // Note: does not alter the actual value of each attribute
  foreach($this->attributes() as $key => $value){
    $clean_attributes[$key] = $database->escape_value($value);
  }
  return $clean_attributes;
}

// replaced with a custom save()
// public function save() {
//   // A new record won't have an id yet.
//   return isset($this->id) ? $this->update() : $this->create();
// }

public function create() {
    global $database;
    // Don't forget your SQL syntax and good habits:
    // - INSERT INTO table (key, key) VALUES ('value', 'value')
    // - single-quotes around all values
    // - escape all values to prevent SQL injection
    $attributes = $this->sanitized_attributes();
  $sql = "INSERT INTO ".self::$table_name." (";
    $sql .= join(", ", array_keys($attributes));
  $sql .= ") VALUES ('";
    $sql .= join("', '", array_values($attributes));
    $sql .= "')";
  if($database->query($sql)) {
    $this->id = $database->insert_id();
    return true;
  } else {
    return false;
  }
}

public function update() {
  global $database;
    // Don't forget your SQL syntax and good habits:
    // - UPDATE table SET key='value', key='value' WHERE condition
    // - single-quotes around all values
    // - escape all values to prevent SQL injection
    $attributes = $this->sanitized_attributes();
    $attribute_pairs = array();
    foreach($attributes as $key => $value) {
      $attribute_pairs[] = "{$key}='{$value}'";
    }
    $sql = "UPDATE ".self::$table_name." SET ";
    $sql .= join(", ", $attribute_pairs);
    $sql .= " WHERE id=". $database->escape_value($this->id);
  $database->query($sql);
  return ($database->affected_rows() == 1) ? true : false;
}

public function delete() {
    global $database;
    // Don't forget your SQL syntax and good habits:
    // - DELETE FROM table WHERE condition LIMIT 1
    // - escape all values to prevent SQL injection
    // - use LIMIT 1
  $sql = "DELETE FROM ".self::$table_name;
  $sql .= " WHERE id=". $database->escape_value($this->id);
  $sql .= " LIMIT 1";
  $database->query($sql);
  return ($database->affected_rows() == 1) ? true : false;

    // NB: After deleting, the instance of User still 
    // exists, even though the database entry does not.
    // This can be useful, as in:
    //   echo $user->first_name . " was deleted";
    // but, for example, we can't call $user->update() 
    // after calling $user->delete().
}

}

?>`

^^This is his complete Photograph() class and below is my photograph class

<?php
//This class will use the database so wil need the database class included
require_once(LIB_PATH.DS.'database.php');
 class Photograph extends DatabaseObject
   {
            public $table_name = "photographs";

public $id;
public $filename;
public $type;
public $size;
public $caption;
public $all_photos = array();

private $temp_path;
protected $upload_dir = "images";

public $errors=array();

protected $upload_errors = array (
UPLOAD_ERR_OK =>            "No errors.",
UPLOAD_ERR_INI_SIZE =>      "Larger than upload_max_filesize.",
UPLOAD_ERR_FORM_SIZE =>     "Larger than form MAX_FILE_SIZE.",
UPLOAD_ERR_PARTIAL =>       "Partial Upload.",
UPLOAD_ERR_NO_FILE =>       "No File",
UPLOAD_ERR_NO_TMP_DIR =>    "No Temp Directory.",
UPLOAD_ERR_CANT_WRITE =>    "Cant write file to disk.",
UPLOAD_ERR_EXTENSION =>     "File uploaded stopped by extension."
);
//Pass in $_FILE['uploaded_file'] as an argument
public function attach_file($file) {
    //Perform error checking on the form params
    if(!$file || empty($file) || !is_array($file)) {
        //error: nothing uploaded or wrong argument
        $this->errors[] = "No file was uploaded.";
        return false;
    } elseif($file['error'] !=0) {
        //error: report what php says went wrong
        $this->errors[] = $this->upload_errors[$file['error']];
        return false;
    } else {
    //Set object attributes to the forms params
    $this->temp_path = $file['tmp_name'];
    $this->filename = basename($file['name']);
    $this->type = $file['type'];
    $this->size = $file['size'];
    //Dont worry about saving anything to database yet
    return true;
    }

}

public function save() {
    //A new record wont have an id yet
    if(isset($this->id)) {
        $this->update();
        //Really just to update the caption
    } else {
        //Make sure there are no errors
        //Cant save if there are pre existing errors
        if(!empty($this->errors)) { return false;}

        //Make suer the caption is not to long for the database
        if(strlen($this->caption) >= 255) {
            $this->errors[] = "The caption can only be 255 characters long.";
            return false;
        }

        //Cant save without the filename and temp location
        if(empty($this->filename) || empty($this->temp_path)) {
            $this->errors[] = "The file location was not available.";
            return false;
        }   

        //Determine the target path
        $target_path = SITE_ROOT .DS. 'public' .DS.$this->upload_dir . DS. $this->filename;

        //Make sure that the file doesn't already exist in that location
        if(file_exists($target_path)) {
            $this->errors[] = "The file {$this->filename} already exists.";
            return false;
        }


        //Attempt to move the file

        if(move_uploaded_file($this->temp_path, $target_path)) {
            //Success
            //Save a corresponding entry to the database
            if($this->create()) {
                //Were done with the temp path variable, The file isn't there any more
                unset($this->temp_path);
                return true;
            }
        } else {
        //Error File was not moved
        $this->errors[] = "The file upload failed, Possibly due to an incorrect permissions on upload folder.";
        return false;
        }

    }
}

public function destroy($id,$filename) {
    //First remove the database entry
    if($this->delete($id)) {
        //Then remove the file
        $target_path = SITE_ROOT.DS.'public'.DS.$this->upload_dir.DS.$filename;
        return unlink($target_path) ? true:false;
    } else {
        //Database delete failed
        return false;
    }

}

public function image_path() {
    return $this->upload_dir.DS;
}

public function size_as_text($file_size) {
    if($file_size < 1024) {
        return "{$file_size} bytes";
    } elseif($file_size < 1048576) {

        $size_kb = round($file_size/1024);
        return "{$size_kb} KB";

    } else {
        $size_mb = round($file_size/1048576, 1);
        return "{size_mb} MB";
    }
}

public function find_all() {
    global $database;
    $result = $this->find_by_sql("SELECT * FROM ".$this->table_name);
    return $result;
}

public function find_all_photos() {
    global $database;
    $query = "SELECT * FROM {$this->table_name}";
    $result = $database->query($query);

    return $result;
}

public function find_by_id($id=0) {
    global $database;

    $result_array = $this->find_by_sql("SELECT * FROM " . $this->table_name . " WHERE id={$database->escape_value($id)} LIMIT 1");
    return !empty($result_array) ? $result_array : false;
}

public function find_by_sql($sql="") {
    global $database;
    $result = $database->query($sql);
    $object_array = $database->fetch_array($result);
    $object = $this->instantiate($object_array);
    //while($row = $database->fetch_array($result)) {
        //$object_array[] = $this->instantiate($row);
    //}
    return $object_array;
}

private function instantiate($record) {

    //Could check if $record exists and is an array

    //Simple long form approach
     //$object = new self;
     $this->id= $record['id'];
     $this->filename    = $record['filename'];
     $this->type    = $record['type'];
     $this->size  = $record['size'];
     $this->caption   = $record['caption'];

    //More dynamic, Short form approach
    //foreach($record as $attribute=>$value) {
        //if($object->has_attribute($attribute)) {
            //$object->$attribute = $value;
        //}
    //}
    //return $object;
}

private function has_attribute($attribute) {
    //get_object_vars returns an assocative array with all attributes
    //Incl. pribate ones as the keys and their current values as the value
    $object_vars = get_object_vars($this);
    //We dont care about the value, we just want to know if the key exists
    //Will return true or false
    return array_key_exists($attribute,$object_vars);
}


public function create() {
    //This is the create method
    global $database;
    //DOnt forget your SQL syntax and good habits
    //INSERT INTO table (key,key) VALUES ('value','value')
    //SIngle-quotes around all values
    //Escape all values to prevent sql injection

    $query = "INSERT INTO {$this->table_name} (";
    $query .= "filename, type, size, caption";
    $query .= ") VALUES ('";
    $query .= $database->escape_value($this->filename) . "', '";
    $query .= $database->escape_value($this->type) . "', '";
    $query .= $database->escape_value($this->size) . "', '";
    $query .= $database->escape_value($this->caption) . "')";

    if($database->query($query)) {
        $this->id = $database->insert_id();
        return true;
    } else {
        return false;
    }
}

public function update() {
    global $database;
    //Dont forget your sql good habits
    //UPDATE table SET key='value', key='value' WHERE condition
    //single quotes around all values
    //Escape all values to prevent sql injection

    $query = "UPDATE {$this->table_name} SET ";
    $query .= "filename='" . $database->escape_value($this->filename) . "', ";
    $query .= "type='" . $database->escape_value($this->type) . "', ";
    $query .= "size='" . $database->escape_value($this->size) . "', ";
    $query .= "caption='" . $database->escape_value($this->caption) . "'";
    $query .= " WHERE id=" . $database->escape_value($this->id);
    $database->query($query);
    return ($database->affected_rows() ==1) ? true : false;

}

public function delete($id=0) {
    global $database;
    //Dont forget good sql habits
    //DELETE FROM table WHERE condition LIMIT 1
    //Escape all values to prevent sql injection 
    //Use limit 1

    $query = "DELETE FROM {$this->table_name} ";
    $query .="WHERE id=" . $database->escape_value($id);
    $query .= " LIMIT 1";
    $database ->query($query);
    return ($database->affected_rows() ==1) ? true:false;

    }

 }
?>

He then went onto using find_all() as to get all the contents from the photographs table on the view_photos.php page

  $photos = Photograph::find_all();
?>
<?php include_layout_template('admin_header.php'); ?>

<h2>Photographs</h2>

<?php echo output_message($message); ?>
<table class="bordered">
  <tr>
    <th>Image</th>
    <th>Filename</th>
    <th>Caption</th>
    <th>Size</th>
    <th>Type</th>
    <th>&nbsp;</th>
  </tr>
<?php foreach($photos as $photo): ?>
  <tr>
    <td><img src="../<?php echo $photo->image_path(); ?>" width="100" />      </td>
    <td><?php echo $photo->filename; ?></td>
    <td><?php echo $photo->caption; ?></td>
    <td><?php echo $photo->size_as_text(); ?></td>
    <td><?php echo $photo->type; ?></td>
        <td><a href="delete_photo.php?id=<?php echo $photo->id; ?    >">Delete</a></td>
   </tr>
<?php endforeach; ?>

As you can see he makes a static call to the find_all() method and then loops through the array to list all of the photos from the database using the captured data stored in the photos variable, using all of the variables inside of the class. below is my find_all() method.

public function find_all() {
    global $database;
    $result = $this->find_by_sql("SELECT * FROM ".$this->table_name);
    return $result;
}

when i do the same thing but with an instance of the object Photograph

$photo_object = new Photograph();
$photos = find_all();

If i try and then do the same loop as he does i just get the same result again and again (There are currently 4 entries in the database and i get the exact same entry about 10 times)

Here is my code which results in that output

<?php require_once("../../includes/initialize.php"); ?>
<?php if(!$session->is_logged_in()) { redirect_to("login.php");} ?>
<?php 

     //This is the class being called
    $photo_object = new Photograph();

     //Find all photos will return the result from the database. We then need to call the fetch array onit
     //$photos = $photo_object->find_all_photos();
    $photos = $photo_object->find_all();
?>


 <?php include_layout_template('admin_header.php'); ?>

<h2>Photographs: List</h2>
<?php echo output_message($message);?>
<table class="bordered">

<tr>
<th>Image</th>
<th>Filename</th>
<th>Caption</th>
<th>Size</th>
<th>Type</th>
<th>&nbsp;</th>
</tr>
  <?php foreach($photos as $photo): ?>
 <tr>
 <td><img src="<?php echo "../" . $photo_object->image_path() .     $photo_object->filename;?>" width="100" /></td>
<td><?php echo $photo_object->filename; ?></td>
 <td><?php echo $photo_object->caption; ?></td>
<td><?php echo $photo_object->size_as_text($photo_object->size); ?></td>
 <td><?php echo $photo_object->type ?></td>
<td><a href="delete_photo.php?id=<?php echo $photo_object->id;?>">Delete</a>    </td>
</tr>
 <?php endforeach; ?>

</table>
<br />
<a href="photo_upload.php">Upload a new photograph</a>

<?php include_layout_template('admin_footer.php'); ?>

The code above outputs

` Photo Gallery: Admin

Photo Gallery: Admin

Photographs: List

<tr>
 <th>Image</th>
<th>Filename</th>
<th>Caption</th>
<th>Size</th>
<th>Type</th>
<th>&nbsp;</th>
 </tr>
 <tr>
<td><img src="../images\bamboo.jpg" width="100" /></td>
<td>bamboo.jpg</td>
 <td>This is a photo of some bamboo</td>
<td>445 KB</td>
 <td>image/jpeg</td>
 <td><a href="delete_photo.php?id=1">Delete</a></td>
</tr>
 <tr>
<td><img src="../images\bamboo.jpg" width="100" /></td>
<td>bamboo.jpg</td>
 <td>This is a photo of some bamboo</td>
<td>445 KB</td>
 <td>image/jpeg</td>
 <td><a href="delete_photo.php?id=1">Delete</a></td>
</tr>
<tr>
<td><img src="../images\bamboo.jpg" width="100" /></td>
<td>bamboo.jpg</td>
<td>This is a photo of some bamboo</td>
 <td>445 KB</td>
 <td>image/jpeg</td>
<td><a href="delete_photo.php?id=1">Delete</a></td>
</tr>
<tr>
<td><img src="../images\bamboo.jpg" width="100" /></td>
<td>bamboo.jpg</td>
<td>This is a photo of some bamboo</td>
<td>445 KB</td>
<td>image/jpeg</td>
<td><a href="delete_photo.php?id=1">Delete</a></td>
</tr>
<tr>
 <td><img src="../images\bamboo.jpg" width="100" /></td>
<td>bamboo.jpg</td>
 <td>This is a photo of some bamboo</td>
<td>445 KB</td>
<td>image/jpeg</td>
<td><a href="delete_photo.php?id=1">Delete</a></td>
 </tr>
<tr>
<td><img src="../images\bamboo.jpg" width="100" /></td>
<td>bamboo.jpg</td>
<td>This is a photo of some bamboo</td>
<td>445 KB</td>
 <td>image/jpeg</td>
<td><a href="delete_photo.php?id=1">Delete</a></td>
</tr>
<tr>
  <td><img src="../images\bamboo.jpg" width="100" /></td>
<td>bamboo.jpg</td>
 <td>This is a photo of some bamboo</td>
 <td>445 KB</td>
 <td>image/jpeg</td>
 <td><a href="delete_photo.php?id=1">Delete</a></td>
</tr>
 <tr>
<td><img src="../images\bamboo.jpg" width="100" /></td>
 <td>bamboo.jpg</td>
<td>This is a photo of some bamboo</td>
 <td>445 KB</td>
<td>image/jpeg</td>
 <td><a href="delete_photo.php?id=1">Delete</a></td> 
 </tr>
 <tr>
 <td><img src="../images\bamboo.jpg" width="100" /></td>
<td>bamboo.jpg</td>
 <td>This is a photo of some bamboo</td>
 <td>445 KB</td>
 <td>image/jpeg</td>
 <td><a href="delete_photo.php?id=1">Delete</a></td>
 </tr>
  <tr>
 <td><img src="../images\bamboo.jpg" width="100" /></td>
 <td>bamboo.jpg</td>
 <td>This is a photo of some bamboo</td>
 <td>445 KB</td>
 <td>image/jpeg</td>
 <td><a href="delete_photo.php?id=1">Delete</a></td>
 </tr>

</table>
 <br />
 <a href="photo_upload.php">Upload a new photograph</a>

 </div>
 <div id="footer">Copyright 2015, Ryan Hadley</div>

 </body>
 </html>
`

Does this method have to be static ? Or am i just not seeing something, I resolved it by writing a new method

public function find_all_photos() {
    global $database;
    $query = "SELECT * FROM {$this->table_name}";
    $result = $database->query($query);

    return $result;
}

This works but i dont use any of the variables inside of the class instead i make a call to the photo array which i create in my foreach loop (foreach($photos as $photo)). Which makes the attributes inside of the class seem very pointless. Did i do this the right way ? Or is there something im just not understanding about objects ?

Thankyou in advance for any help i may get

Happy coding

Answer 1

The code as you have it now, passes $object_array into instantiate .

But instantiate is built to accepts only one row retrieved from the resultset.

If you examine $object_array before passing it, you will know more about why you get the undesired results.

public function find_by_sql($sql="") {
    global $database;
    $result = $database->query($sql);
    $object_array = $database->fetch_array($result);

    // Examine $object_array:
    print '<pre>';
    var_dump($object_array);
    print '</pre>';

    $object = $this->instantiate($object_array);

    return $object_array;
}

About the following commented lines:

 //while($row = $database->fetch_array($result)) {
        //$object_array[] = $this->instantiate($row);
    //}

I suggest uncommenting them and examine the $row 's:

 while( $row = $database->fetch_array($result) ) {

    // Examine $row:
    print '<pre>';
    print_r( $row );
    print '</pre>';

        //$object_array[] = $this->instantiate($row);
 }

About the function instantiate - The way you are using it now, every time it gets called, it sets the properties (id, filename ... etc) of itself. So the last time this function gets called, the values of the properties of the Photograph instance are the same as the ones from the last $record that has been passed to it.

private function instantiate($record) {

    //Could check if $record exists and is an array

    //Simple long form approach
     //$object = new self;
     $this->id= $record['id'];
     $this->filename    = $record['filename'];
     $this->type    = $record['type'];
     $this->size  = $record['size'];
     $this->caption   = $record['caption'];
}

This is a start to provide you insight about why you see 10 times the same result.

I wrote an example to illustrate how you go about to do what you are looking for (determining from your comments):

/**
 * A new class 'Photographs' to 'manage' the collection of photographs:
 **/
class Photographs {

    protected static $table_name="photographs";

    public $photographObjects = array();

    function __construct() {
        // The constructor runs on creation/instantiation of the 'Photographs' object

        print 'Photographs object created...';
    }

    // Retrieves the data and instantiates Photograph objects:
    public function get_photographs() {
        global $database;

        $sql = "SELECT * FROM ". $this->table_name;

        $this->photographObjects = array(); // empty the array before filling it

        $result = $database->query($sql);

        while( $row = $database->fetch_array( $result ) ) {
            $tmpPhotograph = new Photograph();
            $tmpPhotograph->id = $row['id'];
            $tmpPhotograph->filename = $row['filename'];
            // etc etc (or make the 'instantiate' function of the 'Photograph' class public, so you can do:
            // $tmpPhotograph->instantiate($row);
            // Now add a created and initialized object to your array:
            $this->photographObjects[] = $tmpPhotograph;
        }
    }


    // render the photographs:
    public function render_photographs() {

        if ( count($this->photographObjects) > 0 ) { 
            // loop through the objects in the photograpsObjects array:

            foreach ( $this->photographObjects as $tmpPhotograph ) {
                // in this line you can see that public properties (filename), and functions (image_path()) are available:
                print '<img src="../' . $tmpPhotograph->image_path() .     $tmpPhotograph->filename . '" width="100" />';

            }
        } else {
            // Nothing found, inform the user:
            print 'No photographs in array';
        }
    }



}

To use:

$photographManager = new Photographs();
$photographManager->get_photographs(); // retrieve them

$photographManager->render_photographs(); // output them

or when you want to use your line:

<?php foreach($photos as $photo): ?>

You could do this:

<?php foreach( $photographManager->photographObjects as $photo ): ?>

I hope this clears up some things for you.