PHP Judge string length strlen () and Mb_strlen () function

Strlen ()

PHP strlen () function

Definitions and usage

The strlen () function returns the length of the string.

Grammar

Strlen (String)

Parameters: String
Description: Required. Specify the string to check.

The code is as follows	Copy Code
<?php $str = ' Chinese a word 1 characters '; echo strlen ($STR); echo ' <br/> '; Echo Mb_strlen ($str, ' UTF8 '); Output results 14 6 ?>

Result analysis: In strlen calculation, the Chinese character of a UTF8 is 3 lengths, so the length of "a character 1" is 3*4+2=14
When Mb_strlen is computed, the selected inner code is UTF8, and a Chinese character is computed as a length, so the length of the "1" character is 6

Mb_strlen () function

It's important to note that Mb_strlen is not a PHP core function and you need to be sure to load the Php_mbstring.dll in php.ini before you use it to ensure

The "Extension=php_mbstring.dll" line exists and is not commented out, otherwise there is an issue with undefined functions.

The code is as follows	Copy Code
<?php $str = ' Chinese a word 1 characters '; Calculated as follows Echo (strlen ($STR) + Mb_strlen ($str, ' UTF8 '))/2; Echo Output results 10 ?>

The strlen ($STR) value of "Chinese a character 1" is the 14,mb_strlen ($STR) value is 6, you can calculate the "Chinese a character 1 character" occupies the position is 10.

Explain the difference between the two

The code is as follows	Copy Code
<?php How the file is encoded when tested if UTF8 $str = ' Chinese a word 1 characters '; echo strlen ($str). ' <br> ';//14 Echo Mb_strlen ($str, ' UTF8 '). ' <br> ';//6 Echo Mb_strlen ($str, ' GBK '). ' <br> ';//8 Echo Mb_strlen ($str, ' gb2312 '). ' <br> ';//10 ?>

Result analysis: In strlen calculation, the Chinese character of a UTF8 is 3 lengths, so the length of "A word 1" is 3*4+2=14 in Mb_strlen

When calculated, the selected inner code is UTF8, and a Chinese character is computed as a length, so the length of the "1" character is 6.

Although the above function can be simple to solve some of the mixed problems in Chinese and English, but can not be used in reality, I would like to introduce you to the other friends of the better to do

Method.

PHP to obtain in English mixed string length of the implementation code is as follows, 1 Chinese = 1 bits, 2 english = 1 bits, can be modified

The code is as follows

Copy Code

/** * php Get string in English mix length * @param $str string * @param $ $charset string encoding * @return return length, 1 Chinese = 1 bits, 2 english = 1 bits */ function Strlength ($str, $charset = ' utf-8 ') { if ($charset = = ' Utf-8 ') $str = Iconv (' utf-8 ', ' gb2312 ', $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); } Test output length is 15 $str 1 = ' test test test test testing '; $str 2 = ' aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa '; $str 3 = ' AA Test AA Test AA test aaaaaa '; Echo Strlength ($str 1, ' gb2312 '); Echo Strlength ($str 2, ' gb2312 '); Echo Strlength ($str 3, ' gb2312 ');

Intercepting String functions

UTF8 encoding, in UTF8, a Chinese character occupies 3 bytes

The code is as follows	Copy Code
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 ("123 Days to Public 中文版", 0,10);

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

code is as follows	copy code
<?php function Msubstr ($str, $start, $len) {//ȡ $tmpstr = ""; $strlen = $start + $len; if (Preg_match ('/[/d/s]{2,}/', $str)) {$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; } ?>

A function with good coding compatibility

code is as follows

copy code

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; }