suncat100 suncat100 - 7 months ago 12
PHP Question

PHP regex ignore files that start with double __underscore

I have tried, but I simply can't wrap my head around regex in PHP. I need a regex that does the following:


  • ignores files that start with double __underscore. (for example __file.jpg)

  • ignores files that end with "thumb". (for example somethumb.jpg or thumb.jpg)

  • ignores all file types but gif|jpg|png|jpeg



I have the following for now, which seems to fulfill #2 and #3, but not #1:

preg_match(/(?<!thumb)\.(gif|jpg|png|jpeg)$/i, $file)


Any help much appreciated!

Answer

If I understood third point correctly it means that it should end with all these file extensions. Considering this, the following will work

1st Solution

(?!^__|.*thumb\.(gif|jpg|png|jpeg))(^.*)(?=\.(gif|jpg|png|jpeg)$)

Regex Demo

Towards an efficient solution

2nd Solution

^(?!__|.*thumb\.(?:gif|jpg|png|jpeg))(.*(?=\.(?:gif|jpg|png|jpeg)$).*$)

3rd Solution (suggested by Wiktor in comments)

^(?!__|.*thumb\.(?:gif|jpg|png|jpeg))(?=.*\.(?:gif|jpg|png|jpeg)$).*

4th Solution (suggested by Casimir in comments)

^(?!__)(?:[^.\n]*\.)*+(?<!thumb\.)(?:jpe?g|png|gif)$

PHP Code

$re = "/^(?!__|.*thumb\\.(?:gif|jpg|png|jpeg))(?=.*\\.(?:gif|jpg|png|jpeg)$)(.*)/m";
$str = "__abcd.jpg\nthumbabcd.gif\nthumbabcdthumb.jpg\nthumbs.jpg\nsomethumb.jpg\nthumb.jpg\nabcd.jpg\nabcd.jps"; 

preg_match_all($re, $str, $matches);

Ideone Demo