How to intercept the first few digits of a string in php

Two interception methods: 1. Use the substr() function. You only need to set the second parameter of the function to 0 and the third parameter to N to intercept the first N digits of the English string. , syntax "substr(string,0,N)". 2. To use the mb_substr() function, you only need to set the second parameter of the function to 0 and the third parameter to N to intercept the first N digits of the string. The syntax is "mb_substr(string,0,N, Character Encoding)".

The operating environment of this tutorial: Windows 7 system, PHP version 8.1, DELL G3 computer

If you want to intercept strings in PHP, you can use Two functions: substr() function or mb_substr() function.

Method 1: Use the substr() function to intercept the string

The substr() function can intercept characters of a certain length from the specified position of the string.

substr(string,start,length)

Parameters	Description
string	Required . Specifies a part of the string to be returned.
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 - at the first character in the string Start at
length	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

Just set the second parameter of the function to 0 and the third parameter to N to intercept the first N digits of the string.

<?php
header(&#39;content-type:text/html;charset=utf-8&#39;);   
$str="Hello world";
echo "原字符串：".$str."<br>";
echo "截取前1位：".substr($str,0,1)."<br>";
echo "截取前2位：".substr($str,0,2)."<br>";
echo "截取前3位：".substr($str,0,3)."<br>";
echo "截取前4位：".substr($str,0,4)."<br>";
echo "截取前5位：".substr($str,0,5)."<br>";
?>

Note: The substr() function has no problem processing English, but in development we often deal with more Chinese characters. Although the substr() function It can also handle Chinese, but it's not perfect.

<?php
header(&#39;content-type:text/html;charset=utf-8&#39;);   
$str="欢迎来到PHP中文网";
echo "原字符串：".$str."<br>";
echo "截取前1位：".substr($str,0,1)."<br>";
echo "截取前2位：".substr($str,0,2)."<br>";
?>

So how to intercept Chinese characters? You can use the mb_substr() function.

Method 2: Use the mb_substr() function to intercept a string

The mb_substr() function can intercept a specified part of a string, which is different from the substr() function. What's more, the mb_substr() function is not only valid for English characters, but also for Chinese characters.

mb_substr(string,start,length,encoding)

Parameters	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 - at the first character in the string Start at
length	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.

You only need to set the second parameter of the function to 0 and the third parameter to N to intercept the first N digits of the string.

<?php
header(&#39;content-type:text/html;charset=utf-8&#39;);   
$str="欢迎来到PHP中文网";
echo "原字符串：".$str."<br>";
echo "截取前1位：".mb_substr($str,0,1,"utf-8")."<br>";
echo "截取前2位：".mb_substr($str,0,2,"utf-8")."<br>";
?>

<?php
header(&#39;content-type:text/html;charset=utf-8&#39;);   
$str="Hello world";
echo "原字符串：".$str."<br>";
echo "截取前1位：".mb_substr($str,0,1,"utf-8")."<br>";
echo "截取前2位：".mb_substr($str,0,2,"utf-8")."<br>";
?>

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