


1. What is the difference between date and gmdate?
There are two formatting functions in the PHP time function: date() and gmdate(). The description in the official document is:
gmdate() #— Format a GMT/UTC date/time, return Green U.K. Standard Time (GMT).
Let’s take an example first. Our current time zone is +8, so the time returned by the server running the following script should be like this:
The current time is assumed to be 2013-03-14 12:15: 27
echo gmdate('Y-m-d H:i:s'); #With gmdate('Y-m-d H: i:s' time());The output is: 2007-03-14 04:15:27
But this is only the result of running PHP under Linux+Apache. If it is run under Windows, then 2 Each function returns: 2013-03-14 04:15:27.
So, we should give a compatible writing method, use gmdate uniformly, and manually set the current time zone. The writing method is improved as follows:
This way, the correct result is obtained whether under Linux+Apache or Windows , of course, there is another advantage to writing like this. When the website is open to the whole world, then the website user only needs to set the time zone, and the program automatically calculates the time based on the time zone set by the user. Only the current time() is stored in the database for the information release time. The generated time, then the release time seen by users in China +8 time zone is: 2007-03-14 12:15:27, then the release time seen by users in Europe +2 time zone is: 2007-03-14 06:15:27, so that all the times of the information correspond correctly.
2. Will changing the default time zone of PHP affect it?
Each region has its own local time. On the Internet and in radio communications, the problem of time conversion is particularly prominent. The entire earth is divided into twenty-four time zones, each with its own local time. In international radio or network communication situations, for the sake of unification, a unified time is used, called Universal Time Coordinated (UTC), which is a global standard time set by the world time standard. UTC was originally also known as Greenwich Mean Time (GMT, Greenwich Mean Time), which is the same as the local time in London, UK.
The default time zone setting of PHP is UTC time, and Beijing is located in the East Eighth District of the time zone, eight hours ahead of UTC. Therefore, when using functions such as time() in PHP to obtain the current time, the time obtained is always wrong, showing that it is eight hours different from Beijing time. If you want to display Beijing time correctly, you need to modify the default time zone settings, which can be done in the following two ways.
If you are using an independent server and have permission to modify the configuration file, setting the time zone can be completed by modifying the date.timezone attribute in php.ini. We can set the value of this attribute to one of "Asia/Shang", "Asia/Chongqing", "Etc/GMT-8" or PRC, etc., and then the current time obtained in the PHP script is Beijing time. Modify the PHP configuration file as follows:
//Set the default time zone in the configuration file to East 8 District (Beijing time)

php把负数转为正整数的方法:1、使用abs()函数将负数转为正数,使用intval()函数对正数取整,转为正整数,语法“intval(abs($number))”;2、利用“~”位运算符将负数取反加一,语法“~$number + 1”。

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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