Solve the problem of intercepting Chinese strings with PHP

If PHP intercepts a string in English, it is easy. Just use substr directly, and generally there will be no garbled characters. Chinese is a bit troublesome.
Two solutions are given below:
(1) Directly use the Multi-Byte function Just use the mb_substr(); function of the library. The example code is as follows

<?php    
echo mb_substr($str, $start, $length, $encoding);   
echo "<br />";   
?>

This method is simple, fast, safe, beautiful, and tempting. ． ． Anyway, any good words can be used to describe it, but unfortunately my GoDaddy host does not support it, so I have to find another way out
(2) Customize the Chinese string interception function, basically just write a function imitating mb_substr and call it directly, as follows The code I found for me is actually very simple​

<?php    
function  substr_cn($string_input,$start,$length)   
{   
    /* 功能:  
     * 此算法用于截取中文字符串  
     * 函数以单个完整字符为单位进行截取,即一个英文字符和一个中文字符均表示一个单位长度  
     * 参数:  
     * 参数$string为要截取的字符串,  
     * 参数$start为欲截取的起始位置,  
     * 参数$length为要截取的字符个数(一个汉字或英文字符都算一个)  
     * 返回值:  
     * 返回截取结果字符串  
     * */   
    $str_input=$string_input;   
    $len=$length;   
    $return_str="";   
    //定义空字符串   
    for ($i=0;$i<2*$len+2;$i++)   
        $return_str=$return_str." ";   
    $start_index=0;   
    //计算起始字节偏移量   
    for ($i=0;$i<$start;$i++)   
    {   
        if (ord($str_input{$start_index}>=161))          //是汉语        
        {   
            $start_index+=2;   
        }   
        else                                          //是英文   
        {   
            $start_index+=1;   
        }           
    }       
    $chr_index=$start_index;   
    //截取   
    for ($i=0;$i<$len;$i++)   
    {   
        $asc=ord($str_input{$chr_index});   
        if ($asc>=161)   
        {   
            $return_str{$i}=chr($asc);   
            $return_str{$i+1}=chr(ord($str_input{$chr_index+1}));   
            $len+=1; //结束条件加1   
            $i++;    //位置偏移量加1   
            $chr_index+=2;   
            continue;               
        }   
        else    
        {   
            $return_str{$i}=chr($asc);   
            $chr_index+=1;   
        }   
    }       
    return trim($return_str);   
}//en