Question

When using this regex /^[\p{L}\p{N}. -/\\]+$/u in php I get an ‘internal error while using the pattern’ error. It want the matched string to be able to contain backslashes.

Answer 1

$str = '\\';    // = \
$str = '\\\\';  // = \\ (this is what you need for your regex)

So, knowing that, your current regex compiles to:

/^[\p{L}\p{N}. -/\]+$/u

which escapes the “]” character and breaks the regex.

Also your delimiter character “/” and “-” should be escaped inside the regex.

Corrected version:

$regex = '/^[\p{L}\p{N}. \\-\\/\\\\]+$/u';