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) <= $length) {
12. return $string;
13. }
14. $string = str_replace(array('&', '"', '<', '>'), array('&', '"', '<', '>'), $string);
15. $strcut = '';
16. if (strtolower($charset) == 'utf-8') {
17. $n = $tn = $noc = 0;
18. while ($n < strlen($string)) {
19. $t = ord($string[$n]); //ASCII?
20. if($t == 9 || $t == 10 || (32 <= $t && $t <= 126)) {
21. $tn = 1; $n++; $noc++;
22. } elseif (194 <= $t && $t <= 223) {
23. $tn = 2; $n += 2; $noc += 2;
24. } elseif (224 <= $t && $t < 239) {
25. $tn = 3; $n += 3; $noc += 2;
26. } elseif (240 <= $t && $t <= 247) {
27. $tn = 4; $n += 4; $noc += 2;
28. } elseif (248 <= $t && $t <= 251) {
29. $tn = 5; $n += 5; $noc += 2;
30. } elseif ($t == 252 || $t == 253) {
31. $tn = 6; $n += 6; $noc += 2;
32. } else {
33. $n++;
34. }
35. if($noc >= $length) {
36. break;
37. }
38. }
39. if ($noc > $length) {
40. $n -= $tn;
41. }
42. $strcut = substr($string, 0, $n);
43. } else {
44. for ($i = 0; $i < $length; $i++) {
45. $strcut .= ord($string[$i]) > 127 ? $string[$i].$string[++$i] : $string[$i];
46. }
47. }
48. $strcut = str_replace(array('&', '"', '<', '>'), array('&', '"', '<', '>'), $strcut);
49. return $strcut.$dot;
50. }

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. }