php截取字符串函数，php自定义字符串截取方法

2. /**
3. * 方法库-截取字符串
4. * @param string $string 字符串
5. * @param int$length 字符长度
6. * @param string $dot 截取后是否添加...
7. * @param string $charset编码
8. * @return string
9. */
10. public function cutstr($string, $length, $dot = ' ...', $charset = 'utf-8') {
11. if (strlen($string) return $string;
12. }
13. $string = str_replace(array('&', '"', '<', '>'), array('&', '"', ''), $string);
14. $strcut = '';
15. if (strtolower($charset) == 'utf-8') {
16. $n = $tn = $noc = 0;
17. while ($n $t = ord($string[$n]); //ASCII?
18. if($t == 9 || $t == 10 || (32 $tn = 1; $n++; $noc++;
19. } elseif (194 $tn = 2; $n += 2; $noc += 2;
20. } elseif (224 $tn = 3; $n += 3; $noc += 2;
21. } elseif (240 $tn = 4; $n += 4; $noc += 2;
22. } elseif (248 $tn = 5; $n += 5; $noc += 2;
23. } elseif ($t == 252 || $t == 253) {
24. $tn = 6; $n += 6; $noc += 2;
25. } else {
26. $n++;
27. }
28. if($noc >= $length) {
29. break;
30. }
31. }
32. if ($noc > $length) {
33. $n -= $tn;
34. }
35. $strcut = substr($string, 0, $n);
36. } else {
37. for ($i = 0; $i $strcut .= ord($string[$i]) > 127 ? $string[$i].$string[++$i] : $string[$i];
38. }
39. }
40. $strcut = str_replace(array('&', '"', ''), array('&', '"', '<', '>'), $strcut);
41. return $strcut.$dot;
42. }

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例2，php检测字符串是否存在：

2. /**
3. * 方法库-字符串是否存在
4. * @param string $str :字符或字符串
5. * @param string $string :字符串
6. * @return string 例子: $str='34' $string='1234' 返回 TRUE
7. */
8. public function is_str_exist($str, $string) {
9. $string = (string) $string;
10. $str = (string) $str;
11. return strstr($string,$str)===false ? false : true;
12. }

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