As of the writing of this post I'm programing a CMS. I'm including a textbox that allows the user to type in what they would like the 'slug' or name of the page to be. Everything works hunky-dory, provided that the user understands the unaccepted symbols and format for page titles.

I'm working on a regex (using the preg_match function, of course) that converts any thing incompatible into something that is compatible. So for instance, it would convert HEY O to hey-o.php, or hey & O to hey-o.php The problem is, I'm terrible with the regex stuff. No matter how hard I try to understand it, it all goes right over my head.

Can any of you help me out with some kind of regex that converts incompatible results to compatible ones?

Thanks!

PHP Code:

// Get user input
$page = $_POST['page'];
// Strip out unwanted chars and change case
$page = preg_replace('/[^a-z0-9- ]/i', ' ', strtolower($page));
// Remove multiple spaces
while (strpos($page, '  ') !== false) $page = str_replace('  ', ' ', $page);
// Convert spaces to dashes
$page = str_replace(' ', '-', trim($page));
// Check if string is valid
if (strlen($page) > 0)
{
  // Page name is valid
  $page = $page . '.php';
}
else
{
  // Page name is not valid
  $page = '';
} 


No need for reg ex (though it was an excellent answer)

PHP Code:

$var = "HEY O";
$filename = urlencode(strtolower(str_replace(" ", "-", trim($var)))).".php";
//ouputs "hey-o.php", will encode any string so it may be placed into a browser 


Wow! Thanks for the response guys. I honestly didn't think I'd get so much feedback. I found both snippets of code quite helpful, though I am afraid that wayfarer's didn't work... the main problem being that the urlencode() function replaces some symbols with weird stuff that's technically 'browser friendly' but doesn't really look good. So right now, I'm using a variation of mgraphic's code. I'd like to get your input on it.

PHP Code:

$page = preg_replace('/[^a-z0-9-\. ]/i', '', strtolower($page));
$page = str_replace("  ", " ", $page);
$page = str_replace(' ', '-', trim($page));

if(!preg_match('/\.php$/', $page)) {
    $page = $page.".php";
} 


And mgraphic, I'm somewhat curious to know why you used strpos() for replacing the double-spaces with single spaces...

Thanks again!

Great PHP POSIX Regexp explains exactly what you are looking for!

page = preg_replace('/[^a-z0-9-\. ]/i', '', strtolower($page));

I don't think you need to escape a period in a characture class and also since you are forcing the string to lower case, you don't need the "case insensitive" modifier "i" (even though I did the same thing)

$page = str_replace(" ", " ", $page);

I used a while() loop in my example to eleminate all double spaces. In your example above would change 3 spaces to 2 spaces and you still have a double space. I also use the strpos() because it will return an integer if it exists.

while (strpos($page, ' ') !== false) $page = str_replace(' ', ' ', $page);

Okay, cool. I though I needed to escape the period, but I tested it without and it works just fine. I also got rid of the unnecessary modifier at the end of the regex as well as well. Hooray, two less characters!

Thanks for the explanation for the whole while(strpos()) thing. Makes sense now. I also reversed the order of last bit, removing multiple spaces. Now it removes multiple hyphens, which prevents converting something like hey o- mate into hey-o--mate.php. So here's what I've got now.

PHP Code:

$page = preg_replace('/[^a-z0-9-. ]/', '', strtolower($page));
$page = str_replace(' ', '-', trim($page));
while (strpos($page, '--') !== false) $page = str_replace('--', '-', $page);
if(!preg_match('/\.php$/', $page)) {
    $page = $page.".php";
} 


Thanks for all the help!

Originally Posted by stevej

I also reversed the order of last bit, removing multiple spaces. Now it removes multiple hyphens, which prevents converting something like hey o- mate into hey-o--mate.php. So here's what I've got now.

Thats actually a better idea!