How to intercept the first few characters in php

How to intercept the first few characters in php: 1. Use the "substr($str, 0, 3);" method to intercept 3 characters starting from the first character on the left; 2. Use "mb_substr( $str, 0, 2, 'utf-8');" method intercepts Chinese strings.

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Read (intercept substr) the first N characters of a string in PHP Characters or how many characters to start from

<?php 
$str = "123456789";
echo substr($str , 0 , 3);//从左边第一位字符起截取3位字符：结果：123
echo substr($str , 3 , 3);//从左边第3位字符起截取3位字符：结果：456
?>

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

<?php
$rest = substr("abcdef", 0, -1);  // 返回 "abcde"
$rest = substr("abcdef", 2, -1);  // 返回 "cde"
$rest = substr("abcdef", 4, -4);  // 返回 ""
$rest = substr("abcdef", -3, -1); // 返回 "de"
?>

<?php
echo substr(&#39;abcdef&#39;, 1);     // bcdef
echo substr(&#39;abcdef&#39;, 1, 3);  // bcd
echo substr(&#39;abcdef&#39;, 0, 4);  // abcd
echo substr(&#39;abcdef&#39;, 0, 8);  // abcdef
echo substr(&#39;abcdef&#39;, -1, 1); // f
// 访问字符串中的单个字符
// 也可以使用中括号
$string = &#39;abcdef&#39;;
echo $string[0];                 // a
echo $string[3];                 // d
echo $string[strlen($string)-1]; // f
?>

Chinese string interception and length mb_substr()

$str = '我abc是谁';  //utf-8编码的字符串
echo mb_substr($str, 0, 2, 'utf-8'); //输出 我a
 
$str = '我是谁';  //gbk编码的字符串
echo mb_substr($str, 0, 1, 'gbk'); //输出 我

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