PHP 截取字符串函数整理(支持gb2312和utf-8)

<?php 
//截取中文字符串 
function mysubstr($str, $start, $len) { 
$tmpstr = ""; 
$strlen = $start + $len; 
for($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; 
} 
?>

<?php 
//截取utf8字符串 
function utf8Substr($str, $from, $len) 
{ 
return preg_replace(&#39;#^(?:[\x00-\x7F]|[\xC0-\xFF][\x80-\xBF]+){0,&#39;.$from.&#39;}&#39;. 
&#39;((?:[\x00-\x7F]|[\xC0-\xFF][\x80-\xBF]+){0,&#39;.$len.&#39;}).*#s&#39;, 
&#39;$1&#39;,$str); 
} 
?>

<?php 
/* 
Utf-8、gb2312都支持的汉字截取函数 
cut_str(字符串, 截取长度, 开始长度, 编码); 
编码默认为 utf-8 
开始长度默认为 0 
*/ 

function cut_str($string, $sublen, $start = 0, $code = &#39;UTF-8&#39;) 
{ 
if($code == &#39;UTF-8&#39;) 
{ 
$pa = "/[\x01-\x7f]|[\xc2-\xdf][\x80-\xbf]|\xe0[\xa0-\xbf][\x80-\xbf]|[\xe1-\xef][\x80-\xbf][\x80-\xbf]|\xf0[\x90-\xbf][\x80-\xbf][\x80-\xbf]|[\xf1-\xf7][\x80-\xbf][\x80-\xbf][\x80-\xbf]/"; 
preg_match_all($pa, $string, $t_string); 

if(count($t_string[0]) - $start > $sublen) return join(&#39;&#39;, array_slice($t_string[0], $start, $sublen))."..."; 
return join(&#39;&#39;, array_slice($t_string[0], $start, $sublen)); 
} 
else 
{ 
$start = $start*2; 
$sublen = $sublen*2; 
$strlen = strlen($string); 
$tmpstr = &#39;&#39;; 

for($i=0; $i< $strlen; $i++) 
{ 
if($i>=$start && $i< ($start+$sublen)) 
{ 
if(ord(substr($string, $i, 1))>129) 
{ 
$tmpstr.= substr($string, $i, 2); 
} 
else 
{ 
$tmpstr.= substr($string, $i, 1); 
} 
} 
if(ord(substr($string, $i, 1))>129) $i++; 
} 
if(strlen($tmpstr)< $strlen ) $tmpstr.= "..."; 
return $tmpstr; 
} 
} 

$str = "abcd需要截取的字符串"; 
echo cut_str($str, 8, 0, &#39;gb2312&#39;); 
?>

<?php 
/** 
* @package BugFree 
* @version $Id: FunctionsMain.inc.php,v 1.32 2005/09/24 11:38:37 wwccss Exp $ 
* 
* 
* Return part of a string(Enhance the function substr()) 
* 
* @author Chunsheng Wang <wwccss@263.net> 
* @param string $String the string to cut. 
* @param int $Length the length of returned string. 
* @param booble $Append whether append "...": false|true 
* @return string the cutted string. 
*/ 
function sysSubStr($String,$Length,$Append = false) 
{ 
if (strlen($String) < = $Length ) 
{ 
return $String; 
} 
else 
{ 
$I = 0; 
while ($I < $Length) 
{ 
$StringTMP = substr($String,$I,1); 
if ( ord($StringTMP) >=224 ) 
{ 
$StringTMP = substr($String,$I,3); 
$I = $I + 3; 
} 
elseif( ord($StringTMP) >=192 ) 
{ 
$StringTMP = substr($String,$I,2); 
$I = $I + 2; 
} 
else 
{ 
$I = $I + 1; 
} 
$StringLast[] = $StringTMP; 
} 
$StringLast = implode("",$StringLast); 
if($Append) 
{ 
$StringLast .= "..."; 
} 
return $StringLast; 
} 
} 

$String = "book.chinaz.com -- 站长书库、站长教程"; 
$Length = "18"; 
$Append = false; 
echo sysSubStr($String,$Length,$Append); 
?>