PHP Regex for Windows Directory - preg_match

Question

I need to validate a user text entry for a directory based on Windows, there is no directory picker of sort, it is just a text field.

I have written the following Regex using http://regex101.com/ which works adequately for my needs:

^[a-zA-Z]\:[\/,\\].{1,}

Which will match for example the following directories in the online tool:

C:/Users/Charlie/Dropbox
D:/Users/Bob/Quotes
F:/Quotes

The problem is, when using it in my application, preg_match does not match any of the above. It does not return true, and the preg_last_error() returns 0 which also indicates a false return value.

The exact code used is:

if(preg_match('/^[a-zA-Z]\:[\/,\\].{1,}/', $directory)) { }

Any help much appreciated.

Answer 1

You need to use quadruple backslash to match a literal backslash here:

if(preg_match('/^[a-zA-Z]\:[\/,\\\\].{1,}/', 'C:/Users/Charlie/Dropbox')) {
//                             ^^^^

See IDEONE demo

Otherwise, the backslash is just escaping the ] and that ruins the regex character class.

Note that instead of {1,} you can just use + quantifier that means 1 or more occurrences and that you do not have to escape the colon.

I also do not understand why you have a comma in the character class, the character is treated as a literal. I think you just want to match either \\ or / with [\\/,\\\\\\] ? Then, the whole regex would look like

'/^[a-zA-Z]:[\/\\\\].+/'

See another demo