php字符串截取的代码学习

2. //截取utf8字符串
3. function utf8Substr($str, $from, $len)
4. {
5. return preg_replace('#^(?:[\x00-\x7F]|[\xC0-\xFF][\x80-\xBF]+){0,'.$from.'}'.
6. '((?:[\x00-\x7F]|[\xC0-\xFF][\x80-\xBF]+){0,'.$len.'}).*#s',
7. '$1',$str);
8. }
9. ?>

2、UTF-8、GB2312都支持的汉字截取函数

2. function cut_str($string, $sublen, $start = 0, $code = 'UTF-8')
3. {
4. if($code == 'UTF-8')
5. {
6. $pa = "/[\x01-\x7f]|[\xc2-\xdf][\x80-\xbf]|\xe0[\xa0-\xbf][\x80-\xbf]|[\xe1-\xef][\x80-\xbf][\x80-\xbf]|\xf0[\x90-\xbf][\x80-\xbf][\x80-\xbf]|[\xf1-\xf7][\x80-\xbf][\x80-\xbf][\x80-\xbf]/";
7. preg_match_all($pa, $string, $t_string);
9. if(count($t_string[0])- $start > $sublen)return join('', array_slice($t_string[0], $start, $sublen))."...";
10. return join('', array_slice($t_string[0], $start, $sublen));
11. }
12. else
13. {
14. $start = $start*2;
15. $sublen = $sublen*2;
16. $strlen = strlen($string);
17. $tmpstr = '';
19. for($i=0;$i<$strlen;$i++)
20. {
21. if($i>=$start && $i<($start+$sublen))
22. {
23. if(ord(substr($string, $i, 1))>129)
24. {
25. $tmpstr.= substr($string, $i, 2);
26. }
27. else
28. {
29. $tmpstr.= substr($string, $i, 1);
30. }
31. }
32. if(ord(substr($string, $i, 1))>129)$i++;
33. }
34. if(strlen($tmpstr)<$strlen )$tmpstr.= "...";
35. return $tmpstr;
36. }
37. }
38. $str = "abcd需要截取的字符串";
39. echo cut_str($str, 8, 0, 'gb2312');
40. ?>

3、BugFree 的字符截取函数

2. function sysSubStr($String,$Length,$Append = false)
3. {
4. if (strlen($String)<= $Length )
5. {
6. return $String;
7. }
8. else
9. {
10. $I = 0;
11. while ($I < $Length)
12. {
13. $StringTMP = substr($String,$I,1);
14. if (ord($StringTMP)>=224 )
15. {
16. $StringTMP = substr($String,$I,3);
17. $I = $I + 3;
18. }
19. elseif(ord($StringTMP)>=192 )
20. {
21. $StringTMP = substr($String,$I,2);
22. $I = $I + 2;
23. }
24. else
25. {
26. $I = $I + 1;
27. }
28. $StringLast[]= $StringTMP;
29. }
30. $StringLast = implode("",$StringLast);
31. if($Append)
32. {
33. $StringLast .= "...";
34. }
35. return $StringLast;
36. }
37. }
38. $String = "CodeBit.cn -- 简单、精彩、通用";
39. $Length = "18";
40. $Append = false;
41. echo sysSubStr($String,$Length,$Append);
42. ?>