PHP determines the string length strlen() and mb_strlen() functions

strlen()

PHP strlen() function

Definition and usage

strlen() function returns the length of a string.

Syntax

strlen(string)

Parameters: string
Description: Required. Specifies the string to check.

The code is as follows

<?php 
$str=‘中文a字1符‘; 
echo strlen($str); 
echo ‘<br />‘; 
echo mb_strlen($str,‘UTF8‘); 
//输出结果 
//14 
//6 
?>

Result analysis: When calculating strlen, a UTF8 Chinese character is treated as 3 lengths, so the length of "Chinese a character 1 character" is 3*4+2=14
When calculating mb_strlen, select If the internal code is UTF8, a Chinese character will be calculated as a length of 1, so the length of "Chinese a character 1 character" is 6

mb_strlen() function

It should be noted that mb_strlen is not a PHP core function , before use, you need to make sure that php_mbstring.dll is loaded in php.ini, that is, make sure that the line "extension=php_mbstring.dll" exists and is not commented out, otherwise the problem of undefined functions will occur.

The code is as follows

<?php 
$str=‘中文a字1符‘; 
//计算如下 
echo (strlen($str) + mb_strlen($str,‘UTF8‘)) / 2; 
echo 
//输出结果 
//10 
?>

The strlen($str) value of "Chinese a character 1 character" is 14, and the mb_strlen($str) value is 6. Then it can be calculated that the placeholder of "Chinese a character 1 character" is 10.

Explain the difference between the two

The code is as follows

<?php
//测试时文件的编码方式要是UTF8
$str=&#39;中文a字1符&#39;;
echo strlen($str).&#39;<br>&#39;;//14
echo mb_strlen($str,&#39;utf8&#39;).&#39;<br>&#39;;//6
echo mb_strlen($str,&#39;gbk&#39;).&#39;<br>&#39;;//8
echo mb_strlen($str,&#39;gb2312&#39;).&#39;<br>&#39;;//10
?>

Result analysis: When calculating strlen, a UTF8 Chinese character is treated as 3 lengths, so "Chinese a character 1 character" The length is 3*4+2=14. When calculating mb_strlen

, if the internal code is selected as UTF8, a Chinese character will be calculated as a length of 1, so the length of "Chinese a character 1 character" is 6.

Although the above function can simply solve some problems of mixing Chinese and English, it cannot be used in actual practice. Let me introduce other better solutions to my friends

.

The implementation code for PHP to get the length of mixed Chinese and English strings is as follows, 1 Chinese = 1 digit, 2 English = 1 digit, you can modify it yourself

The code is as follows

/*** PHP获取字符串中英文混合长度 * @param $str string 字符串* @param $$charset string 编码* @return 返回长度，1中文=1位，2英文=1位*/function strLength($str,$charset=&#39;utf-8&#39;){if($charset==&#39;utf-8&#39;) $str = iconv(&#39;utf-8&#39;,&#39;gb2312&#39;,$str);$num = strlen($str);$cnNum = 0;for($i=0;$i<$num;$i++){if(ord(substr($str,$i+1,1))>127){$cnNum++;$i++;}}$enNum = $num-($cnNum*2);$number = ($enNum/2)+$cnNum;return ceil($number);}
//测试输出长度都为15$str1 = &#39;测试测试测试测试测试测试测试测&#39;;$str2 = &#39;aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa&#39;;$str3 = &#39;aa测试aa测试aa测试aa测试aaaaaa&#39;;echo strLength($str1,&#39;gb2312&#39;);echo strLength($str2,&#39;gb2312&#39;);echo strLength($str3,&#39;gb2312&#39;);

Intercept string function

UTF8 encoding, in In UTF8, one Chinese character occupies 3 bytes

The code is as follows

function msubstr($str, $start, $len) {
 $tmpstr = "";
 $strlen = $start + $len;
 for($i = 0; $i < $strlen; $i++){
  if(ord(substr($str, $i, 1)) > 127){
   $tmpstr.=substr($str, $i, 3);
   $i+=2;
  }else
   $tmpstr.= substr($str, $i, 1);
 }
 return $tmpstr;
}
echo msubstr("一二三天下致公english",0,10);

GB2312 encoding, in gb2312, one Chinese character occupies 2 bytes

The code is as follows

<?php
function msubstr($str, $start, $len) {   //ȡ
   $tmpstr = "";
   $strlen = $start + $len;
   if(preg_match(&#39;/[/d/s]{2,}/&#39;,$str)){$strlen=$strlen-2;}
   for($i = 0; $i < $strlen; $i++) {
       if(ord(substr($str, $i, 1)) > 0xa0) {
           $tmpstr .= substr($str, $i, 2);
           $i++;
       } else
           $tmpstr .= substr($str, $i, 1);
     }
   return $tmpstr;
 }
  
?>

Compatible The code of the good function

is as follows

function cc_msubstr($str, $start=0, $length, $charset="utf-8", $suffix=true)
{
 if(function_exists("mb_substr"))
  return mb_substr($str, $start, $length, $charset);
 elseif(function_exists('iconv_substr')) {
  return iconv_substr($str,$start,$length,$charset);
 }
 $re['utf-8']   = "/[/x01-/x7f]|[/xc2-/xdf][/x80-/xbf]|[/xe0-/xef][/x80-/xbf]{2}|[/xf0-/xff]
[/x80-/xbf]{3}/";
 $re['gb2312'] = "/[/x01-/x7f]|[/xb0-/xf7][/xa0-/xfe]/";
 $re['gbk']   = "/[/x01-/x7f]|[/x81-/xfe][/x40-/xfe]/";
 $re['big5']   = "/[/x01-/x7f]|[/x81-/xfe]([/x40-/x7e]|/xa1-/xfe])/";
 preg_match_all($re[$charset], $str, $match);
 $slice = join("",array_slice($match[0], $start, $length));
 if($suffix) return $slice."…";
 return $slice;
}