Today I will share with you how to learn in detail the infinite classification method in php. Friends who are learning PHP can refer to it.
There are roughly three methods of unlimited classification in php,
1. The database performs unique indexing by setting the parent class ID, and thenuses 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:
-- -- 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', '网站首页'), (2, '0-1', 'Linux OS'), (3, '0-1', 'Apache服务器'), (4, '0-1', 'MySQL数据库'), (5, '0-1', 'PHP脚本语言'), (6, '0-1-2', 'Linux 系统教程'), (7, '0-1-2', 'Linux 网络技术'), (8, '0-1-2', 'Linux 安全基础'), (9, '0-1-2-7', 'Linux LAMP'), (10, '0-1-3-10', 'apache Server');Here is the description of catpath The - link symbol is not fixed, you can choose special symbols such as;
2. PHP code implementation:
$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 ( $query ) ) { /** * 第一种展示方法 */ /*$space = str_repeat ( ' ', count ( explode ( '-', $row ['abspath'] ) ) - 1 ); echo $space . $row ['name'] . '<br>';*/ /** * 第二种展示方法 */ $space = str_repeat ( ' ', count ( explode ( '-', $row ['abspath'] ) ) - 1 ); $option .= '<option value="' . $row ['id'] . '">' . $space . $row ['name'] . '</option>'; } echo '<select name="opt">' . $option . '</select>';Above rendering:
1. The concat function is used in the database query field. If you don’t understand, 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
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实现方法:1、使用“sleep(延迟秒数)”语句,可延迟执行函数若干秒;2、使用“time_nanosleep(延迟秒数,延迟纳秒数)”语句,可延迟执行函数若干秒和纳秒;3、使用“time_sleep_until(time()+7)”语句。

php字符串有下标。在PHP中,下标不仅可以应用于数组和对象,还可应用于字符串,利用字符串的下标和中括号“[]”可以访问指定索引位置的字符,并对该字符进行读写,语法“字符串名[下标值]”;字符串的下标值(索引值)只能是整数类型,起始值为0。

php除以100保留两位小数的方法:1、利用“/”运算符进行除法运算,语法“数值 / 100”;2、使用“number_format(除法结果, 2)”或“sprintf("%.2f",除法结果)”语句进行四舍五入的处理值,并保留两位小数。

判断方法:1、使用“strtotime("年-月-日")”语句将给定的年月日转换为时间戳格式;2、用“date("z",时间戳)+1”语句计算指定时间戳是一年的第几天。date()返回的天数是从0开始计算的,因此真实天数需要在此基础上加1。

在php中,可以使用substr()函数来读取字符串后几个字符,只需要将该函数的第二个参数设置为负值,第三个参数省略即可;语法为“substr(字符串,-n)”,表示读取从字符串结尾处向前数第n个字符开始,直到字符串结尾的全部字符。

方法:1、用“str_replace(" ","其他字符",$str)”语句,可将nbsp符替换为其他字符;2、用“preg_replace("/(\s|\ \;||\xc2\xa0)/","其他字符",$str)”语句。

查找方法:1、用strpos(),语法“strpos("字符串值","查找子串")+1”;2、用stripos(),语法“strpos("字符串值","查找子串")+1”。因为字符串是从0开始计数的,因此两个函数获取的位置需要进行加1处理。


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