How to intercept Chinese string from the first digit in php

In PHP, you can use the mb_substr() function to intercept a Chinese string from the specified position. This function can intercept a substring of a specified length starting from a specified position of a string, and set the character encoding; syntax "mb_substr (specified string, interception starting position, interception length, character encoding)".

The operating environment of this tutorial: windows7 system, PHP7.1 version, DELL G3 computer

When processing strings, sometimes we The string needs to be intercepted. In PHP, intercepting strings can be achieved through PHP's predefined functions substr() and mb_substr()

Among them, the substr() function is not very friendly to Chinese processing, while the mb_substr() function is used for Intercept Chinese string.

mb_substr() function can intercept a specified part from a string. Different from the substr() function, the mb_substr() function is not only valid for English characters, but also for Chinese characters. Its syntax format is as follows :

mb_substr ( string $str , int $start [, int $length = NULL [, string $encoding = mb_internal_encoding() ]] ) : string

Parameter	Description
str	Required. Extracts a substring from this string.
start	Required. Specifies where in the string to begin. Positive number - starts at the specified position in the string Negative number - starts at the specified position from the end of the string 0 - starts at the specified position in the string Starting at one character
length	is optional. Specifies the length of the string to be returned. The default is until the end of the string. Positive number - Returns from the position of the start parameter Negative number - Returns from the end of the string
encoding	Optional. Character Encoding. If omitted, the internal character encoding is used.

Return value: Returns the extracted part of the string, returns FALSE if it fails, or returns an empty string.

Example: Use the mb_substr() function to intercept a Chinese string of specified length.

<?php
header("Content-type:text/html;charset=utf-8");
$str = &#39;欢迎访问php中文网，一个在线学习编程的网站。&#39;;
echo mb_substr($str,4,null,"utf-8").&#39;<br>&#39;;
echo mb_substr($str, -19,null,"utf-8").&#39;<br>&#39;;
echo mb_substr($str, 4, 6,"utf-8").&#39;<br>&#39;;
echo mb_substr($str, 4, -16,"utf-8").&#39;<br>&#39;;
echo mb_substr($str, -19, -13,"utf-8").&#39;<br>&#39;;
echo mb_substr($str, -19, 6,"utf-8").&#39;<br>&#39;;
var_dump(mb_substr($str, 40,null,"utf-8"));
var_dump(mb_substr($str, 4, null,"utf-8"));
?>

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