using regex to define an array of allowed $_GET values

cprowitt

I'm very very new to php and i've been using this code from a tut i found online for one of my pages. I have a feeling there is a very simple solution for what I want to do. The code explains itself so i'll get right into it...

<?php
// 1. Define an array of allowed $_GET values:
    $pass = array('p01s01','p02s01','p03s01','p04s01','p06s01','p07s01','p10s01','p12s01','p14s01');

// 2. If the page is allowed, include it:
    if (in_array($_GET['id'], $pass)) {
     include ('includes/AprilStories/' . $_GET['id'] . '.php');
    }

// 3. If there is no $_GET['id'] defined, then serve the homepage:
    elseif (!isset($_GET['id'])) {
     include ("includes/blank.php");
    }

// 4. If the page is not allowed, send them to an error page:
    else {
     // This sends the 404 header:
      header("HTTP/1.0 404 Not Found");
     // This includes the error page:
      include ("includes/error.php");
} 
?>

I simply want to use regex for the very first part of the code where it defines an array of allowed $_GET values. Right now i have every page 'id' listed. I'd like to simplify that with regex so it will match "p[:digit:]{2}s[:digit:]{2}"

I've tried everything and still cant get it to work....i think im trying to put the ereg in the wrong place.

also here is the url for the page im trying to use regex on... www.obsrep.com/businessjournal/stories.php

additionally i was trying to put the ereg() in the array()....not sure if that was right

thanks!

CoderDan

I think you should skip using the $pass array completly, and just use:

if ( ereg( "p[:digit:]{2}s[:digit:]{2}", $_GET['id'] ) ) {

edit: you should additionally add a file_exists check:

if ( ereg( "p[:digit:]{2}s[:digit:]{2}", $_GET['id'] ) && file_exists('includes/AprilStories/' . $_GET['id'] . '.php') ) {

or similar

dagon

ereg is being discontinued use PCRE Functions

cprowitt

so the PCRE equivalent of what CoderDan wrote would be....

I mean i'd like to use the latest and greatest version of regex.

CoderDan

ereg( "p[:digit:]{2}s[:digit:]{2}", $_GET['id'] )
// would become:
preg_match( '/p[\d{2}s\d{2}/', $_GET['id'] )

.. i think... i didn't test it and i prefer to test my regular expressions 😛

but yeah, i prefer perl regular expressions myself also, I'd just copied what you had as your regexp 😛

cprowitt

i've never seen preg_match. all those slashes kind of scare me..haha

if ereg works is there really a better way to do it? or is this just another case of theres no wrong way just different ways?

dagon

ereg will not exist in future releases of php, if you use it then move servers or upgrade your script will fail

CoderDan

perl-compatable regular expressions (PCRE) are mostly the same as POSIX Extended, for beginner at least, the main difference is PCRE has a delimited in front and back of teh expression, and the most common delimeter is a forward slash
you can use either if you're writing for yourself and arent planning to change environments.
there's a lot of discussion indicating one is faster than the other, and the commonly accepted view is that PCRE is superior.
If you're just getting into regular expressions I'd reccomend just using PCRE as the most commonly supported, as you'll find the most help for it out .. here, i guess, but you're fine to just stick to your ereg if you prefer.

cprowitt

im just starting so i'll take your advice and go with the scary slashes. I'm sure i'll get used to them after awhile. Can you recommend any reading material for regex beginners?

also, POSIX character classes wont work with PCRE?...maybe im not quite understanding.

CoderDan

reccomended reading for PCRE: http://us3.php.net/pcre

cprowitt

ok i've done this...

<?php
// Define allowed $_GET values and if allowed, include it:
    if (preg_match( '/p[\d{2}s\d{2}/', $_GET['id'] ) && file_exists('includes/AprilStories/' . $_GET['id'] . '.php')) {
     include ('includes/AprilStories/' . $_GET['id'] . '.php');
    }

// If there is no $_GET['id'] defined, then serve the homepage:
    elseif (!isset($_GET['id'])) {
     include ("includes/blank.php");
    }

// If the page is not allowed, send them to an error page:
    else {
     // This sends the 404 header:
      header("HTTP/1.0 404 Not Found");
     // This includes the error page:
      include ("includes/error.php");
} 
?>

...but it returns the error.php include.

cprowitt

nm, there was an extra "[" in that regex line

thanks guys for all your help!

CoderDan

i typoed on it, there's an extra [ in there, get rid of it 🙂 should be:
/p\d{2}s\d{2}/
and it actually probably should actually be:
/^{p\d{2}s\d{2}$/}
to ensure there is no lead/trail space.

dagon

i use this site to test my regX RegExr: Online Regular Expression Testing Tool

CoderDan

oh, that's a pretty neat site, dagon, thanks for the link! 🙂

cprowitt

while we're at it how can i use preg to match the current month in those 'includes/AprilStories" lines? So i dont have to change the code every month to for example "includes/MayStories"

CoderDan

you could use preg match for the month name, but in that case you may as well just use an array and straight comparisons, as there is no pattern code for month names, so you'd pretty much have to put the array into the match pattern anyway. (Yes, is can be done with regexp, but there's no reason to 😛)

cprowitt

oh, i see what you're saying. Thanks anyway!