want explanation..

[karthikanov24]

IN THE FOLLOWING PHP FILE(FILE TO DISPLAY CATEGORIES IN ADMIN MODULE OF SHOPPING CART), WHAT IS THE USE OF $i VARIABLE,$class ,'row1'.

WHAT IS THE USE  OF IF CONDITIONS AT  ($i%2),

if ($cat_parent_id == 0) {
		$cat_name = "<a href=\"index.php?catId=$cat_id\">$cat_name</a>";
	}

	if ($cat_image) {
		$cat_image = WEB_ROOT . 'images/category/' . $cat_image;
	} else {
		$cat_image = WEB_ROOT . 'images/no-image-small.png';
	}	
/////////////////////////PHPFILE//////////////////////////////

<?php
if (!defined('WEB_ROOT')) {
exit;
}

if (isset($_GET['catId']) && (int)$_GET['catId'] >= 0) {
$catId = (int)$_GET['catId'];
$queryString = "&catId=$catId";
} else {
$catId = 0;
$queryString = '';
}

// for paging
// how many rows to show per page
$rowsPerPage = 5;

$sql = "SELECT cat_id, cat_parent_id, cat_name, cat_description, cat_image
        FROM tbl_category
	WHERE cat_parent_id = $catId
	ORDER BY cat_name";
$result     = dbQuery(getPagingQuery($sql, $rowsPerPage));
$pagingLink = getPagingLink($sql, $rowsPerPage);
?>
<p> </p>
<form action="processCategory.php?action=addCategory" method="post"  name="frmListCategory" id="frmListCategory">
<table width="100%" border="0" align="center" cellpadding="2" cellspacing="1" class="text">
  <tr align="center" id="listTableHeader"> 
   <td>Category Name</td>
   <td>Description</td>
   <td width="75">Image</td>
   <td width="75">Modify</td>
   <td width="75">Delete</td>
  </tr>
  <?php
$cat_parent_id = 0;
if (dbNumRows($result) > 0) {
$i = 0;

while($row = dbFetchAssoc($result)) {
	extract($row);

	if ($i%2) {
		$class = 'row1';
	} else {
		$class = 'row2';
	}

	$i += 1;

	if ($cat_parent_id == 0) {
		$cat_name = "<a href=\"index.php?catId=$cat_id\">$cat_name</a>";
	}

	if ($cat_image) {
		$cat_image = WEB_ROOT . 'images/category/' . $cat_image;
	} else {
		$cat_image = WEB_ROOT . 'images/no-image-small.png';
	}		
?>
  <tr class="<?php echo $class; ?>"> 
   <td><?php echo $cat_name; ?></td>
   <td><?php echo nl2br($cat_description); ?></td>
   <td width="75" align="center"><img src="<?php echo $cat_image; ?>"></td>
   <td width="75" align="center"><a href="javascript:modifyCategory(<?php echo $cat_id; ?>);">Modify</a></td>
   <td width="75" align="center"><a href="javascript:deleteCategory(<?php echo $cat_id; ?>);">Delete</a></td>
  </tr>
  <?php
} // end while


?>
  <tr> 
   <td colspan="5" align="center">
   <?php 
   echo $pagingLink;
   ?></td>
  </tr>
<?php	
} else {
?>
  <tr> 
   <td colspan="5" align="center">No Categories Yet</td>
  </tr>
  <?php
}
?>
  <tr> 
   <td colspan="5"> </td>
  </tr>
  <tr> 
   <td colspan="5" align="right"> <input name="btnAddCategory" type="button" id="btnAddCategory" value="Add Category" class="box" onClick="addCategory(<?php echo $catId; ?>)"> 
   </td>
  </tr>
</table>
<p> </p>
</form>

 

[Ken2k7]

The $i, $class, 'row1', 'row2' and $i % 2 lines are all used to accomplish one thing - alternate rows.

 

So you have a table, and you want alternating colors or whatever for each row. So row1 and row2 are CSS classes for <TR> HTML tag. The variable $i starts at 0. $i % 2 checks if the number is even or odd, but as $i increments, it alternates between the two, which sets $class to either 'row1' or 'row2'.

 

So at first, when $i = 0, %i % 2 == 0, so $class is set to 'row2' because if (0) is false and so it goes to the else clause. See where it says $i += 1? Well that increments $i to be 1. The next time the while loop runs, $i will be 1. $i % 2 == 1. if (1) is true so $class is now 'row1'. Then $i becomes 2. $i % 2 == 0 and it keeps on going like that until the while loop stops.

 

The '%' sign is called a modulus. It means remainder after division. So dividing 1 by 2 gives you a remainder of 1. 2 divided by 2 has a remainder of 0.

 

I hope that helped. Let me know if you need any further clarification.

[karthikanov24]

WHY WE DECLARE $cat_parent_id = 0;

 

 

WHAT  DOES THE EXPRESSIONS AT FOLLOWING MEANS???

 

 

if ($cat_parent_id == 0) {

$cat_name = "<a href=\"index.php?catId=$cat_id\">$cat_name</a>";

}

 

if ($cat_image) {

$cat_image = WEB_ROOT . 'images/category/' . $cat_image;

} else {

$cat_image = WEB_ROOT . 'images/no-image-small.png';

}

 

[Ken2k7]

You mean the one inside the while loop?

 

If so, then one important statement is extract($row). It takes an array and assigns the values to appropriate variable names. One of them is $cat_parent_id. (See the SQL.) It checks if the $cat_parent_id is 0, if so, it gives it a $cat_name. $cat_image is gotten from extract($row) as well.

[karthikanov24]

I MEAN THE $cat_parent_id = 0; OUTSIDE THE WHILE LOOP

 

WHATS THE USE OF IT?

[Ken2k7]

Probably the same use as inside the while loop. I assume $cat_parent_id is defined somewhere. I honestly can't tell you much in that context. But I guess you can take it down and see what changes.