Web developers notes,programming tutorials.

In drupal we can create custom validation for the custom fields created using the CCK module for

content types. We can create a validation wizard or field validation for each content type

seperatly. This requires two modules CCK and CCK_validation.

To add a validation field to a content type, go to administer > content >
content types, select the content type you want to add to, and click on the
‘add field’ tab. One of the field types available should be ‘Validation’, and it
should have one bullet point under it, labelled ‘Textarea PHP Code’. If you select
this, give your field a name, and submit the form, you will get to the
configuration page for your new computed field.

Suppose imagine a content type named “Book” and it has custom field “ISBN”. In the ‘Textarea PHP Code’ of the Validation field we can write a validation code like the one below.

if (!isbn_format($node->field_text[0][’value’])){
form_set_error(’field_text’,'The ISBN is not in a valid format.’);
}

function isbn_format($code)
{

if(!preg_match(”/[a-zA-Z]/”,substr($code,0,3),$match))
return false;
if(!is_numeric(substr($code,0,7)))
return false;
return true;
}

Consider the following tree structure:

Food
|
————————-
| |
Fruit Meat
——— ———-
| | | |
Red Yellow Beef Pork

Step 1:
=====
Start Numbering the nodes. Start from the root node. Each node will have left ane right values.
For Eg: Assign “1″ to the left side of root node “Food”. Assign “2″ to the left side of “Fruit” node and “3″ to the left side of “Red” node.

[1] Food [14]
|
——————————
| |
[2] Fruit [7] [8] Meat [13]
————- ——————
| | | |
[3] Red [4] [5] Yellow [6] [9] Beef [10] [11] Pork [12]

Note: The Right Value of the root node “Food” will have the highest value.
This method of walking around the tree and counting nodes is called the ‘modified preorder tree traversal’ algorithm

Database Structure and Value will be as follows:

Parent Title lft rgt
==============================
Food 1 14
Food Fruit 2 7
Fruit Red 3 4
Fruit Yellow 5 6
Food Meat 8 13
Meat Beed 9 10
Meat Pork 11 12

EXAMPLES:
========

1. if you want the ‘Fruit’ subtree, you’ll have to select only the nodes with a left value between 2 and 7. In SQL, that would be:

SELECT * FROM tree WHERE lft BETWEEN 2 AND 7 ORDER BY lft ASC;

If you add and delete rows from your table, your table probably won’t be in the right order. We should therefore order the rows by their left value

[ORDER BY lft ASC].

2. if you want the ‘Meat’ subtree, you’ll have to select only the nodes with a left value between 8 and 13. In SQL, that would be:

SELECT * FROM tree WHERE lft BETWEEN 8 AND 13 ORDER BY lft ASC;

ADD A NODE AT MIDDLE:
==================

If we want to add a node at the middle position, say for eg, a child node for the node “Red” , we have to follow the following steps:

1. First, we’ll have to make some space by changing the right value and left value of “Red” and the other following node values.

[1] Food [16]
|
——————————
| |
[2] Fruit [9] [10] Meat [15]
————- ——————
| | | |
[3] Red [6] [7] Yellow [8] [11] Beef [12] [13] Pork [14]
|
[4] Cherry [5]

2. Following query is used to update the right and left values:

UPDATE tree SET rgt=rgt+2 WHERE rgt>4;
UPDATE tree SET lft=lft+2 WHERE lft>4;

we need to add 2 values to both left and right. For eg: Previously, the right value for node “Red” is [4] and now it is changed to [6]. Similarly

we have to do for all other nodes.

3. After Altering the node values we have to insert a new node. Following is the query used to insert a new node:

INSERT INTO tree SET lft=4, rgt=5, title=’Cherry’;

ADDING A NODE AT END:
===================

Following SQL query must be executed to Add a node at the end ie a child node to the node “Pork”.

UPDATE tree SET rgt=rgt+2 WHERE rgt>14;
INSERT INTO tree SET lft=14, rgt=15, title=’New’;

SAMPLE CODE TO DISPLAY TREE STRUCTURE:
==================================

0) {
// check if we should remove a node from the stack
while ($right[count($right)-1]
A right values of the nodes need to kept in a stack to show the tree structure:
$right = array();

Add the right value of node to the stack each time when we start with the children of a node:
$right[] = $row[’rgt’];

All children of that node have a right value that is less than the right value of the parent, so by comparing the right value of the current node with

the last right node in the stack, we can see if we’re still displaying the children of that parent.
while ($right[count($right)-1]

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* Write blog articles about the site.
* Post to Drupal Showcase and DrupalSites.net.
* Go to Google Webmaster Tools and made sure there were no errors with 404 and 403 pages, etc.
* Test site on search engine simulators (crawlers).
* Add title tags on the site (supposedly better for search engines).
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* Add robots.txt.
* Send Google and Yahoo a feedback email asking why the site wasn’t being indexed.
* Create unique description and keywords meta tags on every page.
* Add the site to web directories.
* Adding a Google Sitemap
*click link on Google Webmaster Tools called “Submit a reinclusion request”. and submit the form asking to be reincluded in their index.