MySQL "SET NAMES xxx" character set problem analysis
There is also an article about Apache and PHP coding: http://www.phpchina.com/bbs/thread-13860-1-1.html
Recently received training from BBT to build a voting system. The system code is not difficult, but my time is mainly spent on studying character sets and
Encoding above. The encoding (character set) issues of the MySQL and Apache systems made me rack my brains and suffer a lot.
on these issues onlineThe solutions are scattered and one-sided. Most of them provide solutions without explaining why. So I will summarize what I have gained in the past few days to avoid
Latecomers will take detours. This article is a little helpful for PHP writing (after reading it, you will know how to make your PHP program available in most spaces
The provider’s server displays normally), but more help lies in the installation and settings of the network server.
Let’s talk about MySQL’s character set first. Under Windows, you can modify the
in my.ini
Copy content to clipboard code:
# CLIENT SECTION
[mysql]
default-character-set=utf8
# SERVER SECTION
[mysqld]
default-character-set=utf8
These two fields are used to change the default character set of the database. The first is the client's default character set, and the second is the server's default character set
. Suppose we set both to utf8, and then enter “show variebles like
” in the MySQL Command Line Client"character_set_%";", you can see the following characters:
character_set_client latin1
character_set_connection latin1
character_set_database utf8
character_set_results latin1
character_set_server utf8
character_set_system utf8
The utf8 among them changes with our settings above. At this time, if we read data from the database through a PHP program using UTF-8,
It is most likely a string of "?????" or other garbled characters. After searching online for a long time, the solution is simple. After connecting to the database, read
Before fetching data, first execute a query "SET NAMES UTF8", which is
in PHP
Copy content to clipboard code:
mysql_query("SET NAMES UTF8");
It can be displayed normally (as long as the characters of the information in the database are normal). Why is this happening? What exactly is this query "SET NAMES UTF8"
What does it do?
Go to the MySQL command line and enter "SET NAMES UTF8;", then execute "show variebles like "character_set_%";",
Found those variables "character_set_client", "character_set_connection", and
that were originally latin1The values of "character_set_results" have all changed to utf8. It turns out that these three variables are causing trouble. Check the manual, the above sentence is equal to:
Copy content to clipboard code:
SET character_set_client = utf8;
SET character_set_results = utf8;
SET character_set_connection = utf8;
Take a look at the functions of these 3 variables:
Information input path: client→connection→server;
Information output path: server→connection→results.
In other words, each path goes through three character set encoding changes. Taking the garbled output as an example, the utf8 data in the server is passed in
The connection is converted to latin1, the incoming results are converted to latin1, and the utf-8 page converts the results again. If the two character sets are not compatible
For example, latin1 and utf8, the conversion process is irreversible and destructive. So it can't be turned back.
But it should be stated here that the effect of "SET NAMES UTF8" is only temporary, and MySQL will return to the default after restarting.
Next, let’s talk about the configuration of MySQL on the server. Don’t we have to add “SET NAMESUTF8” every time we read and write to the database
to ensure consistent encoding of data transmission? Can I configure MySQL so that the three variables default to the character set we want? Hand
It’s not mentioned in the booklet, and I couldn’t find the answer online. Therefore, from a server configuration perspective, there is no way to omit that line of code.
Summary: In order to allow your webpage to display normally on more servers, add "SET NAMES UTF8", even if you don't have it yet
Even if you add this sentence, you can access it normally.

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。

php判断有没有小数点的方法:1、使用“strpos(数字字符串,'.')”语法,如果返回小数点在字符串中第一次出现的位置,则有小数点;2、使用“strrpos(数字字符串,'.')”语句,如果返回小数点在字符串中最后一次出现的位置,则有。

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。

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。

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。


Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

AI Hentai Generator
Generate AI Hentai for free.

Hot Article

Hot Tools

mPDF
mPDF is a PHP library that can generate PDF files from UTF-8 encoded HTML. The original author, Ian Back, wrote mPDF to output PDF files "on the fly" from his website and handle different languages. It is slower than original scripts like HTML2FPDF and produces larger files when using Unicode fonts, but supports CSS styles etc. and has a lot of enhancements. Supports almost all languages, including RTL (Arabic and Hebrew) and CJK (Chinese, Japanese and Korean). Supports nested block-level elements (such as P, DIV),

SublimeText3 Linux new version
SublimeText3 Linux latest version

Notepad++7.3.1
Easy-to-use and free code editor

PhpStorm Mac version
The latest (2018.2.1) professional PHP integrated development tool

Dreamweaver CS6
Visual web development tools
