强大的文件类型检测函数 php代码

2. /**
3. * @access public
4. * @param string filename 文件名
5. * @param string limit_ext_types 允许的文件类型，用|包围的类型如：|gif|txt|
6. * @return string
7. * by http://bbs.it-home.org
8. */
9. function check_file_type($filename, $limit_ext_types = ''){
10. $extname = strtolower(substr($filename, strrpos($filename, '.') + 1));
11. if ($limit_ext_types &&
12. stristr($limit_ext_types, '|' . $extname . '|') === false){
13. return '';
14. }
16. $str = $format = '';
18. $file = @fopen($filename, 'rb');
19. if ($file){
20. $str = @fread($file, 0x400); // 读取前 1024 个字节
21. @fclose($file);
22. }
23. else{
24. $format=$extname;
25. }
27. if ($format == '' && strlen($str) >= 2 ){
28. if (substr($str, 0, 4) == 'MThd' && $extname != 'txt'){
29. $format = 'mid';
30. }
31. elseif (substr($str, 0, 4) == 'RIFF' && $extname == 'wav'){
32. $format = 'wav';
33. }
34. elseif (substr($str ,0, 3) == "xFFxD8xFF"){
35. $format = 'jpg';
36. }
37. elseif (substr($str ,0, 4) == 'GIF8' && $extname != 'txt'){
38. $format = 'gif';
39. }
40. elseif (substr($str ,0, 8) == "x89x50x4Ex47x0Dx0Ax1Ax0A"){
41. $format = 'png';
42. }
43. elseif (substr($str ,0, 2) == 'BM' && $extname != 'txt'){
44. $format = 'bmp';
45. }
46. elseif ((substr($str ,0, 3) == 'CWS' || substr($str ,0, 3) == 'FWS')
47. && $extname != 'txt'){
48. $format = 'swf';
49. }
50. elseif (substr($str ,0, 4) == "xD0xCFx11xE0"){ // D0CF11E == DOCFILE == Microsoft Office Document
51. if (substr($str,0x200,4) == "xECxA5xC1x00"
52. || $extname == 'doc'){
53. $format = 'doc';
54. }
55. elseif (substr($str,0x200,2) == "x09x08" || $extname == 'xls'){
56. $format = 'xls';
57. }
58. elseif (substr($str,0x200,4) == "xFDxFFxFFxFF"
59. || $extname == 'ppt'){
60. $format = 'ppt';
61. }
62. }
63. elseif (substr($str ,0, 4) == "PKx03x04"){
64. $format = 'zip';
65. }
66. elseif (substr($str ,0, 4) == 'Rar!' && $extname != 'txt'){
67. $format = 'rar';
68. }
69. elseif (substr($str ,0, 4) == "x25PDF"){
70. $format = 'pdf';
71. }
72. elseif (substr($str ,0, 3) == "x30x82x0A"){
73. $format = 'cert';
74. }
75. elseif (substr($str ,0, 4) == 'ITSF' && $extname != 'txt'){
76. $format = 'chm';
77. }
78. elseif (substr($str ,0, 4) == "x2ERMF"){
79. $format = 'rm';
80. }
81. elseif ($extname == 'sql'){
82. $format = 'sql';
83. }
84. elseif ($extname == 'txt'){
85. $format = 'txt';
86. }
87. }
89. if ($limit_ext_types &&
90. stristr($limit_ext_types, '|' . $format . '|') === false){
91. $format = '';
92. }
94. return $format;
95. }

复制代码