PHP unlimited classification: three methods of non-function recursive calling! _ PHP Tutorial-php Tutorial

PHP unlimited classification: three methods of non-function recursive calling !. There are roughly three methods for php unlimited classification. 1. the database performs a unique index by setting the parent class ID, and then uses the recursive call of the function to implement unlimited classification; 2. there are roughly three methods for database design to use a specific php unlimited classification,

1. the database performs a unique index by setting the parent class ID, and then uses the recursive call of the function to implement unlimited classification;

2. the database is designed to be arranged in a specific format, and then use mysql to query the key function: concat. Program implementation is relatively simple;

3. The third type is not too familiar. it seems that algorithms and data structures need to be used for sorting.

Today, I am mainly sharing the second method. at the beginning, I also found a lot of information, which is really hard to understand. But I finally figured it out, so I wrote down the article and hoped that this article could help you.

I. database design:　　

The code is as follows:

--
-- Table structure for table 'Category'
--
Create table if not exists 'Category '(
'Id' int (11) not null AUTO_INCREMENT,
'Catpath' varchar (255) default null,
'Name' varchar (255) default null,
Primary key ('id ')
) ENGINE = MyISAM default charset = utf8 AUTO_INCREMENT = 11;
--
-- Dumping data for table 'Category'
--
Insert into 'category '('id', 'catpath', 'name') VALUES
(1, '0', 'Website '),
(2, '0-1', 'Linux OS '),
(3, '0-1', 'Apache server '),
(4, '0-1', 'MySQL database '),
(5, '0-1', 'php scripting language '),
(6, '0-1-2 ', 'Linux system tutorial '),
(7, '0-1-2 ', 'Linux network techno '),
(8, '0-1-2 ', 'Linux security basics '),
(9, '0-1-2-7 ', 'Linux LAMP '),
(10, '0-1-3-10 ', 'Apache server ');

Here, The-link symbol of catpath is not fixed and can be selected, and other special symbols.
II. PHP code implementation:

The code is as follows:

$ Conn = mysql_connect ('localhost', 'root ','');
Mysql_select_db ('test', $ conn );
Mysql_query ('set names utf8 ');
$ SQL = "select id, concat (catpath, '-', id) as abspath, name from category order by abspath ";
$ Query = mysql_query ($ SQL );
While ($ row = mysql_fetch_array ($ query )){
/**
* Method 1
*/
/* $ Space = str_repeat ('', count (explode ('-', $ row ['abspath'])-1 );
Echo $ space. $ row ['name'].'
';*/
/**
* Method 2
*/
$ Space = str_repeat ('', count (explode ('-', $ row ['abspath'])-1 );
$ Option. =''. $ Space. $ row ['name'].'';
}
Echo''. $ Option .'';

On:

　　　　

Note the following key points:
1. the concat function is used to query fields in the database. if you are not familiar with this function, you can google it.
2. in the second place, str_repeat in php is used to cleverly set spaces.
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Databases, 1. the database performs unique indexes by setting the parent class ID, and then uses the recursive call of the function to implement unlimited classification. 2. the database is designed through a specific...