How to query what string starts with in php

Two implementation methods: 1. Use the substr() function to query the header character. You only need to set the second parameter of the function to 0 and the third parameter to N to get the beginning of the string. N characters, syntax "substr(string,0,N)". 2. Use the mb_substr() function to query the header characters. You only need to set the second parameter of the function to 0 and the third parameter to N to get the N characters at the beginning 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

What does the php query string start with, is the query What are the characters (substring) at the head of the string. We can do this by getting the header characters.

Method 1: Use substr() to query (get) the header characters

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

substr(string,start,length)

Just set the second parameter of the function to 0 and the third parameter to N to get the first N characters 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 "开头的1个字符：".substr($str,0,1)."<br>";
echo "开头的2个字符：".substr($str,0,2)."<br>";
echo "开头的3个字符：".substr($str,0,3)."<br>";
?>

Note: The substr() function has no problem processing English, but in development we often deal with Chinese There are many characters. Although the substr() function can also handle Chinese, it is 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 "开头的1个字符：".substr($str,0,1)."<br>";
echo "开头的2个字符：".substr($str,0,2)."<br>";
echo "开头的3个字符：".substr($str,0,3)."<br>";
?>

In the substr() function, a GB2312 encoded Chinese character occupies two characters in length, and a UTF-8 encoded Chinese characters are three characters long.

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

Method 2: Use the mb_substr() function to query (get) the header characters

The mb_substr() function can intercept a specified part from a string, and substr () function is different in that, The mb_substr() function is not only valid for English characters, but also for Chinese characters.

mb_substr(string,start,length,encoding)

• string, start, length: have the same effect as the three parameters of the substr() function, please refer to them.

• encoding: is an optional parameter used to set the 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 get the first N characters 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 "开头的1个字符：".mb_substr($str,0,1,"utf-

8")."<br>";
echo "开头的2个字符：".mb_substr($str,0,2,"utf-

8")."<br>";
?>

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