SIMPLE regular expression

[Joshua4550]

Hey guys, I REALLY can't get my head around this RegEx shit.. not quite sure why though, anything I try doesn't work.. even with this simple regex i need.

 

Can anybody tell me the regex for any number, letter, period or underscore?

 

I think I'll be using eregi for it, unless you suggest something more efficient.

This is because i need to check a string to see whether it contains anything that is NOT this, then I can give the user an error.

Thanks.

[foxsoup]

Hey there.  If you want to check a string for a character which isn't a letter, number, period or underscore then you could use the following:

 

if (preg_match('/[^a-z0-9\._]/i', $yourstring) > 0) {
// contains bad characters
}

 

Basically the '^' character means find matches that aren't in the square brackets.  Then we're defining a range of all letters (a to z), all numbers (0 to 9), a period (which needs a backslash in front of it to escape it, since a period is a regex metacharacter) and an underscore.  The 'i' at the end of the regex, outside of the delimiters, means to make the search case-insensitive (so a-z also covers A-Z).

 

The reason I've used preg rather than ereg for this is that the ereg functions have been deprecated as of PHP 5.3, and will be removed from PHP 6, so using preg should extend the lifespan of your code somewhat. 

[Joshua4550]

Thanks alot, and thank you for explaining it nicely.

 

I'll replace all uses of ereg or eregi with preg_match in my sources, thanks for telling me about that!