PCRE... and i thought i understood it
 

Ok so here are a few examples of what i am trying to allow

2E2X1
3C051
5B174

First spot needs to be a number, second a letter, third a number again, forth any of the following: X,1,3,5,7,9 and then fifth a number again.

I am also trying to allow it to have "DEP" and "Civ" as an option to type as well but would like the capitalization to hold. So here is my expression but i don't fully understand it as much as i thought i did

^[0-9][A-Z][0-9][X13579][0-9]|[DEP]|[Civ]$

Any help would be much appreciated.

Something like:

Your biggest error seems to be that you have square brackets around the "DEP" and "Civ", this tells that it shoud have 1 of the characters D, E or P (and C, i, v for the 2nd), instead of matching the word "DEP"

ok so with that it allows me to put depP and civV... the extra characters and wrong capitals (although i guess nit picky of me) are not what i am trying to do. With [A-Z] it doesn't allow lower case... how can i do that for DEP and Civ?

As long as you aren't using the "i" modifier, it should be case sensitive.

I am using that identical PCRE expression above and i can put more characters then just DEP and casing isn't being followed

I wish I understood this better... that doesn't work either. Doesn't allow for any combo of lower/upper letters with dep or civ... it also doesn't allow for any combo of the first sequence either. no 2E251 or anything.

Try Also I use a program called Regex Coach to test things like this before I use it in PHP.

I think there is no hope for me... not working either. I had tried regex coach i will have to try it again