What to do if php substr intercepts garbled strings

php substr interception string garbled solution: 1. Use the "mb_substr()" of the mbstring extension library to intercept, the syntax "mb_substr(string, starting position, character length, "character encoding")"; 2. Use the function in ecshop to intercept strings encoded in UTF-8.

The operating environment of this article: windows7 system, PHP8 version, DELL G3 computer

In PHP program development, string interception is often performed For example, when outputting a list of information, the title should not be too long. When printing an article summary, 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 Chinese garbled characters, because 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 not accurate, substr() abruptly "saws" a Chinese character in half, causing the broken character to pull the following... together to make a 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 string, specified by the parameters start and length.

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

Example:

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

There is no problem with English. We test a Chinese

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

The result of intercepting characters is definitely not the result we want. This appears in PHP The garbled Chinese characters of substr may cause the program to fail to run normally. 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 multiple lines must be added at the end of mb_substr()/mb_strcut. A parameter 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.

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

If the last encoding parameter is not specified, three bytes will be used as one Chinese character. This is the characteristic of utf-8 encoding. If the utf-8 character set description is added, it will be one character. Intercepted for the unit.

When using, pay attention to the encoding of the php file and the encoding when the web page is displayed. 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 is not so easy to use. 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.

function sub_str($str, $length = , $append = true)
{
  $str = trim($str);
  $strlength = strlen($str);
  if ($length == || $length >= $strlength)
  {
    return $str; //截取长度等于或大于等于本字符串的长度，返回字符串本身
  }
  elseif ($length < ) //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 < )
    {
      $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(&#39;mb_substr&#39;))
  {
    $newstr = mb_substr($str, , $length, EC_CHARSET);
  }
  elseif (function_exists(&#39;iconv_substr&#39;))
  {
    $newstr = iconv_substr($str, , $length, EC_CHARSET);
  }
  else
  {
    //$newstr = trim_right(substr($str, , $length));
    $newstr = substr($str, , $length);
  }
  if ($append && $str != $newstr)
  {
    $newstr .= &#39;...&#39;;
  }
  return $newstr;
}

Okay, that’s all the description in this article. I believe it will bring you something. The above code is also very simple. If you don’t understand anything, please leave me a message. I will Will reply to everyone as soon as possible.

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