[SOLVED] inheriting constructor class from parent

[garry27]

I have a LISTING class which I used to display a list of gigs up until recently. Having reorganised the class to so that I can make it a superclass for all listing types, I then created a GIG_LISTING class and transfered the methods that apply to this class across.

 

This is something which I have done a few times previously without a problem. Unlike before, this time I've written the superclass so that child classes use the __constructor class of the parent class.

 

I can reference variable which are set in the constructor class fine. The problem rises when I assign the return of a method (which is unique to the parent class) to an attribute inside the construcor, it always returns as NULL.

 

Any idea why this is occuring?

 

Thanks.

 

 

 

 

[rhodesa]

i don't completely understand what you mean. can you post a code sample?

[discomatt]

This may help

 

Note:  Parent constructors are not called implicitly if the child class defines a constructor. In order to run a parent constructor, a call to parent::__construct() within the child constructor is required. 

[garry27]

I'm not declaring a constructor in the child- I want it to inherit it from the parent.

 

I've done some more checks and I can access at least a few methods from the parent class via the parent constructor, via the child class. But not this method:

 

  private function assignSortByValue()
  {
  	##assigns sortBy value from 'sortBy' GET param if name in $this->columns else assigns first value in $this->columns
    if($_GET['sortBy']) {
  	  while($column = current($this->columns)) {
  	    if($_GET['sortBy'] == $column) {
  		  $this->sortByValue = $column;
  	    }
  	    next($this->columns);
  	  }
    }
    else {
      $this->sortByValue = current($this->columns);
    }	
  }

 

which is called like this:

 

  function __construct($columns...)
  {
  	//used for defining db columns and secondary, table columns
    $this->columns = $columns;

 

 

 

 

[garry27]

If I do this:

 

  function __construct($columns,...)
  {
    $this->columns = $columns;
    $this->assignSortByValue();
    var_dump($this->sortByValue);
...

 

.. I get the right value but if I try and access

$this->sortByValue

inside the child, I get a NULL value.

 

Why's this?

[rhodesa]

i don't see any problems. can you post the entire code for both classes?

[garry27]

Ok, here's goes:

 

<?php

//echos a data table with headers. includes other class

class LISTING
{ 
  //table presentation	
  public $columns;  // arr(GET value=>Db value...) - defined on new object
  public $tdColl;
  public $tblAttr;
  public $trAttr='';
  public $tblNum = 1;
  //data presentation - defined in constructor
  public $resultsPerPage;
  public $numPages;
  public $maxPages;
  public $currPage; 
  private $sortByValue; 
  public $filterBy;      //GET name i.e. 'County'
  private $filterByGetValue;    //current filter GET value i.e. 'CountyDurham'
  public $filterByDbValue;   //current filter DB value i.e. 'County Durham'
  public $sqlFilterBy;
  public $firstRecordOnPage;
  
  
  function __construct($columns,$tblAttr,$resultsPerPage,$maxPages,$filterBy,$filterByDbValues)
  {
  	//used for defining db columns and secondary, table columns
    $this->columns = $columns;
  	$this->tblAttr = $tblAttr;	
  	$this->resultsPerPage = $resultsPerPage;
  	$this->maxPages = $maxPages;
  	$this->filterBy = $filterBy;
  	
  	$this->assignSortByValue();
  	$this->assignFilterByParams($filterByDbValues);

  	#set current page number
  	if(!$_GET['Page']) {
  	  $this->currPage = 1;
  	}
  	else {
  	  $this->currPage = $_GET['Page'];
  	}

    $numRecords = $this->getNumRecords();  
    
    ###get number of pages
    $x = $numRecords / $this->resultsPerPage;
    if(is_float($x)) {
      $this->numPages = $x + 1;
    }
    else {
      $this->numPages = $x;	
    }    

  	#get first and last record numbers
  	$this->firstRecordOnPage = $this->currPage * $this->resultsPerPage - $this->resultsPerPage;                                      
  }	
  
  
  
  //fixed
  private function assignFilterByParams($filterValues)
  {
  	##returns filter value for $this->filterBy GET param
    while($column = current($filterValues)) {
  	  if($_GET[$this->filterBy] == $column) {
  	    $this->filterByDbValue = key($filterValues);
  	    $this->filterByGetValue = $column;
  	  }
  	  next($filterValues);
    }
    return;
  }
  
  //fixed
  private function assignSortByValue()
  {
  	##assigns sortBy value from 'sortBy' GET param if name in $this->columns else assigns first value in $this->columns
    if($_GET['sortBy']) {
  	  while($column = current($this->columns)) {
  	    if($_GET['sortBy'] == $column) {
  		  $this->sortByValue = $column;  	
  		  
  	    }
  	    next($this->columns);
  	  }
    }
    else {
      $this->sortByValue = current($this->columns);
    }
    return;
  }

  
  
  function getNumRecords()
  {
    $LDM = new LISTING_DATA_MAPPER;
       
  	if($_GET[$this->filterBy]) {
  	  $this->filterBySql = "AND GA_Town.county = '".$this->filterByDbValue."'";
      return $LDM->fetchNumGigsByCounty($this->filterByDbValue);
    }
    else{
      return $LDM->fetchNumGigsByRegion();
    } 
  }

  
  function getDbListingsObjects()
  {
    $LDM = new LISTING_DATA_MAPPER();    
  	$dbListingsObjects = $LDM->fetchGigListings($this->filterBySql,$this->sortByValue,
  	                                            $this->firstRecordOnPage,$this->resultsPerPage);    
return $dbListingsObjects;                                                   
  }
  

  //fixed
  function getListings()
  {
    return  "<table ".$this->tblAttr.">"
              .$this->getListingsThead()
              .$this->getListingsTbody()
        ."\n </table>\n"
              .$this->getPageNumbers();
  }


  function getListingsTHead()
  {
    $i = 1;
  	$columns = array_flip($this->columns);
    unset($columns['endTime']);  //no longer required

    while($txt = current($columns))
    {
      $thCells .=  "\n <th id='gigsTd$i'><a class='sortHeaderLink' href='".$_SERVER['PHP_SELF'].
                                                                      "?".$this->filterBy."=".$this->filterByGetValue.
                                                                      "&sortBy=".key($columns)."'>$txt</a></th>";
      
      $i++;
      next($columns);
  	}
    return "\n <thead>
                 <tr>".$thCells."</tr>
            \n </thead>";          	
  }
  
  
  function getListingsTbody()
  {
  	$listingsObjects = $this->getDbListingsObjects();  
    while($result = $listingsObjects->fetch_object()) 
    {   	
      $cells = null;
      $columns = $this->columns;
      unset($columns['End']); //remove end column
     
      foreach($columns as $key=>$val) 
      {
        if($val == 'date') {
          $timestamp = strtotime($result->$val);  
          $result->$val = date("D, j M" ,$timestamp);
        }
        elseif($val == 'entryFee') {
          if(empty($result->$val)) {
            $result->$val = 'Free';
          }
        }
        elseif($val == 'startTime') {  //merge start/end into one column
          $result->$val = $result->$val . '-' . $result->endTime;	
        }
        elseif(!$result->$val) {
          $result->$val = 'N/A';
        }
    $cells .= "\n <td>" .$result->$val. "</td>";   
      }
      $rows .= "\n <tr". $this->trAttr.">" .$cells . "</tr>";
}
  	return "<tbody>".$rows."</tbody>";
  }
  
  //fixed
  private function getPageNumbers() 
  {
  	
  	###build pages hyperlinks
  	for($i=1; $i<=$this->numPages; $i++ ) 
  	{
  	  //assign bold style to current page
  	  if($i == $this->currPage){
  	  	$listContent = "<li style='font-weight:bold;'>$i</li>";
  	  }
  	  else{
  	    $listContent = "<a href='/Browse-Gigs.php?".$this->filterBy."=".$this->filterByGetValue."&Page=".$i.
  	                                            "&sortBy=".$this->sortByValue."' 
  	                      title='Gig Results Page $i link'>$i</a>";
  	  }
  	  $numbers .= "<li>$listContent</li>";
  	}
    return "<div id='pageNumbers'>
              <ul>"
                .$numbers
            ."</ul>
            </div>";	
  }
  

}
?>

 

 

<?php

class GIG_LISTING extends LISTING
{ 

  function getNumRecords()
  {
    $LDM = new LISTING_DATA_MAPPER;
       
  	if($_GET[$this->filterBy]) {
  	  $this->filterBySql = "AND GA_Town.county = '".$this->filterByDbValue."'";
      return $LDM->fetchNumGigsByCounty($this->filterByDbValue);
    }
    else{
      return $LDM->fetchNumGigsByRegion();
    } 
  }

  
  function getDbListingsObjects()
  {
    $LDM = new LISTING_DATA_MAPPER();    
  	$dbListingsObjects = $LDM->fetchGigListings($this->filterBySql,$this->sortByValue,
  	                                            $this->firstRecordOnPage,$this->resultsPerPage);    
  
  //	var_dump($this->filterBySql);
  var_dump($this->sortByValue);
  	//var_dump($this->firstRecordOnPage);
  	//var_dump($this->resultsPerPage);
  	
return $dbListingsObjects;                                                   
  }
  
  

  function getListingsTHead()
  {
    $i = 1;
  	$columns = array_flip($this->columns);
    unset($columns['endTime']);  //no longer required

    while($txt = current($columns))
    {
      $thCells .=  "\n <th id='gigsTd$i'><a class='sortHeaderLink' href='".$_SERVER['PHP_SELF'].
                                                                      "?".$this->filterBy."=".$this->filterByGetValue.
                                                                      "&sortBy=".key($columns)."'>$txt</a></th>";
      
      $i++;
      next($columns);
  	}
    return "\n <thead>
                 <tr>".$thCells."</tr>
            \n </thead>";          	
  }
  
  
  function getListingsTbody()
  {
  	$listingsObjects = $this->getDbListingsObjects();  
    while($result = $listingsObjects->fetch_object()) 
    {   	
      $cells = null;
      $columns = $this->columns;
      unset($columns['End']); //remove end column
     
      foreach($columns as $key=>$val) 
      {
        if($val == 'date') {
          $timestamp = strtotime($result->$val);  
          $result->$val = date("D, j M" ,$timestamp);
        }
        elseif($val == 'entryFee') {
          if(empty($result->$val)) {
            $result->$val = 'Free';
          }
        }
        elseif($val == 'startTime') {  //merge start/end into one column
          $result->$val = $result->$val . '-' . $result->endTime;	
        }
        elseif(!$result->$val) {
          $result->$val = 'N/A';
        }
    $cells .= "\n <td>" .$result->$val. "</td>";   
      }
      $rows .= "\n <tr". $this->trAttr.">" .$cells . "</tr>";
}
  	return "<tbody>".$rows."</tbody>";
  }

  
  
  
  
  
  
  
  
  
  
  


}

?>

[rhodesa]

ah, in the parent class you have:

  private $sortByValue; 

which will block the child class from being able to access it. use 'protected' instead, which will block scripts from accessing it, but child classes can still use it.

 

  protected $sortByValue; 

[garry27]

Ye, I just saw it before! I don't know why it doesn't throw back a error or a warning though, like they do when you try and access a method that's out of 'scope'.

 

Thanks for your help!!!!!