Three ways of infinite classification in PHP. Recursive calls of non-functions! _PHP Tutorial

There are roughly three ways to classify unlimited PHP,

1. The database performs unique indexing by setting the parent class ID, and then uses recursive calls of functions to achieve unlimited classification;

　2. The database design is arranged in a specific format, and then uses mysql to query the key function: concat. The program implementation is relatively simple;

3. I don’t know much about the third type. It seems that algorithms and data structures are used for arrangement.

Today I will mainly share the second method. I found a lot of information at the beginning and it was indeed difficult to understand. But I finally figured it out, so I wrote down an essay, hoping that this article can help everyone.

1. Database design: 　

Copy code 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', 'Homepage'),
(2, '0-1', 'Linux OS'),
(3, '0-1', 'Apache server'),
(4, '0-1', 'MySQL database'),
(5, '0-1', 'PHP script language'),
(6, '0-1-2', 'Linux system tutorial'),
(7, '0-1-2 ', 'Linux network technology'),
(8, '0-1-2', 'Linux security basics'),
(9, '0-1-2-7', 'Linux LAMP' ),
(10, '0-1-3-10', 'apache Server');

It is explained here that the - link symbol of catpath is not fixed and can be selected; and other special symbols.
2. PHP code implementation:

Copy code 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 ( $query ) ) {
/**
* The first display method
*/
/*$space = str_repeat ( ' ', count ( explode ( '-', $row ['abspath'] ) ) - 1 );
echo $space . $ row ['name'] . '
';*/
/**
* The second display method
*/
$space = str_repeat ( ' ', count ( explode ( '-', $row [' abspath'] ) ) - 1 );
$option .= '' . $space . $row ['name'] . '';
}
echo '' . $option . '';

The rendering above:

　

There are several key points to note here:
1. The concat function is used in the database query field. If you don’t understand anything, you can google it.
2. The second place mainly uses str_repeat in php to cleverly set spaces.
If there are any errors, please email: chenghuiyong1987@gmail.com or leave a message

http://www.bkjia.com/PHPjc/324119.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/324119.htmlTechArticleThere are roughly three methods for unlimited classification in PHP. 1. The database uniquely indexes by setting the parent class ID, and then uses the function Recursive calls to achieve unlimited classification; 2. Database design through specific...