Solving the problem of garbled Chinese characters when PHP substr intercepts strings

In PHP program development, string interception operations are often performed. For example, when outputting an information list, the title should not be too long. When printing an article abstract, a series of string interception operations must also be performed. When encountering these requirements, we often think of using the substr() method to achieve it. substr() is more suitable for intercepting all-English strings

But as long as Chinese characters appear in the string, it may cause PHP substr is garbled in Chinese. Because of Chinese UTF-8 encoding, each Chinese character occupies 3 bytes, while GB2312 occupies 2 bytes, and English occupies 1 byte. The number of intercepted digits is inaccurate. substr() abruptly "saws" a Chinese character. " in half, causing the broken character to pull the following .. together to make one word, so PHP substr Chinese garbled characters appear.

substr --- Get part of the string

Syntax: string substr (string string, int start [, int length])
Description:
substr() returns a part of the string, which is determined by the parameter start and length specified.
If start is a positive number, the returned string will start from the start character of string.
Example:

<?php
$rest = substr ("abcdef", 1); // returns "bcdef"
$rest = substr ("abcdef", 1, 3); // returns "bcd"
?>

If start is a negative number, the returned string will start from the start character at the end of string.
Example:

<?php
$rest = substr ("abcdef", -1); // returns "f"
$rest = substr ("abcdef", -2); // returns "ef"
$rest = substr ("abcdef", -3, 1); // returns "d"
?>

If the parameter length is given and it is a positive number, the returned string will be length characters from start.
If the parameter length is given and it is a negative number, the returned string will end at the length-th character from the end of the string.
Example:

<?php
$rest = substr ("abcdef", 1, -1); // returns "bcde"
?>

There is no problem with English, we test a Chinese

Example:

<?php
$rest = substr ("中国人", 1, -1); // returns "fdsafsda" 就是乱码了
?>

This kind of result of intercepting characters is definitely not the result we want, this kind of PHP substr Chinese Garbled characters may cause the program to fail to run properly. There are two main solutions:

1. Use mb_substr() of the mbstring extension library to intercept, so that garbled characters will not appear.

You can use the function mb_substr()/mb_strcut(). The usage of mb_substr()/mb_strcut() is similar to substr(), except that one more parameter needs to be added at the end of mb_substr()/mb_strcut to set the encoding of the string. , but most servers do not open php_mbstring.dll. You need to open php_mbstring.dll in php.ini.

Example:

<?php
    echo mb_substr("php中文字符encode",0,4,"utf-8");
?>

If the last encoding parameter is not specified, it will be three bytes for one Chinese character. This is the characteristic of utf-8 encoding. If you add the utf-8 character set description, so , intercepted in units of one character.

When using it, please pay attention to the encoding of the php file and the encoding when displaying the web page. To use this mb_substr method, you need to know the encoding of the string in advance. If you don't know the encoding, you need to judge. The mbstring library also provides mb_check_encoding to check the string encoding, but it is not perfect yet.

PHP comes with several string interception functions, among which substr and mb_substr are commonly used. When the former processes Chinese, GBK is 2 length units and UTF is 3 length units. After the latter specifies encoding, one Chinese character is 1 length unit.

substr sometimes cuts off 1/3 of Chinese or half of Chinese and displays garbled characters. Relatively speaking, mb_substr is more suitable for us to use. But sometimes mb_substr doesn't seem so useful. For example, if I want to display the brief information of a small picture, 5 Chinese characters are just right. If there are more than 5 characters, just intercept the first 4 and add "...". This is no problem when processing Chinese, but when processing English or numbers, this interception will be too short. .

Second, write the interception function yourself, but the efficiency is not as high as using the mbstring extension library. The following is a function in ecshop that intercepts strings encoded in UTF-8.

Example :

function sub_str($str, $length = 0, $append = true)
{
    $str = trim($str);
    $strlength = strlen($str);
 
    if ($length == 0 || $length >= $strlength)
    {
        return $str;  //截取长度等于0或大于等于本字符串的长度，返回字符串本身
    }
    elseif ($length < 0)  //如果截取长度为负数
    {
        $length = $strlength + $length;//那么截取长度就等于字符串长度减去截取长度
        if ($length < 0)
        {
            $length = $strlength;//如果截取长度的绝对值大于字符串本身长度，则截取长度取字符串本身的长度
        }
    }
 
    if (function_exists('mb_substr'))
    {
        $newstr = mb_substr($str, 0, $length, EC_CHARSET);
    }
    elseif (function_exists('iconv_substr'))
    {
        $newstr = iconv_substr($str, 0, $length, EC_CHARSET);
    }
    else
    {
        //$newstr = trim_right(substr($str, 0, $length));
        $newstr = substr($str, 0, $length);
    }
 
    if ($append && $str != $newstr)
    {
        $newstr .= '...';
    }
 
    return $newstr;
}

The above introduces the solution to the problem of garbled Chinese characters when intercepting strings with PHP substr, including the relevant content. I hope it will be helpful to friends who are interested in PHP tutorials.