Regular Expression to match unlimited number of options - php

Question

I want to be able to parse file paths like this one:
/var/www/index.(htm|html|php|shtml)
into an ordered array:
array("htm", "html", "php", "shtml")
and then produce a list of alternatives:
/var/www/index.htm
/var/www/index.html
/var/www/index.php
/var/www/index.shtml
Right now, I have a preg_match statement that can split two alternatives:
preg_match_all ("/\(([^)]*)\|([^)]*)\)/", $path_resource, $matches);
Could somebody give me a pointer how to extend this to accept an unlimited number of alternatives (at least two)? Just regarding the regular expression, the rest I can deal with.
The rule is:
The list needs to start with a ( and close with a )
There must be one | in the list (i.e. at least two alternatives)
Any other occurrence(s) of ( or ) are to remain untouched.
Update: I need to be able to also deal with multiple bracket pairs such as:
/var/(www|www2)/index.(htm|html|php|shtml)
sorry I didn't say that straight away.
Update 2: If you're looking to do what I'm trying to do in the filesystem, then note that glob() already brings this functionality out of the box. There is no need to implement a custom solutiom. See #Gordon's answer below for details.

Answer 1

I think you're looking for:
/(([^|]+)(|([^|]+))+)/
Basically, put the splitter '|' into a repeating pattern.
Also, your words should be made up 'not pipes' instead of 'not parens', per your third requirement.
Also, prefer + to * for this problem. + means 'at least one'. * means 'zero or more'.

Answer 2

Not exactly what you are asking, but what's wrong with just taking what you have to get the list (ignoring the |s), putting it into a variable and then explodeing on the |s? That would give you an array of however many items there were (including 1 if there wasn't a | present).

Answer 3

Non-regex solution :)
<?php
$test = '/var/www/index.(htm|html|php|shtml)';
/**
*
* #param string $str "/var/www/index.(htm|html|php|shtml)"
* #return array "/var/www/index.htm", "/var/www/index.php", etc
*/
function expand_bracket_pair($str)
{
// Only get the very last "(" and ignore all others.
$bracketStartPos = strrpos($str, '(');
$bracketEndPos = strrpos($str, ')');
// Split on ",".
$exts = substr($str, $bracketStartPos, $bracketEndPos - $bracketStartPos);
$exts = trim($exts, '()|');
$exts = explode('|', $exts);
// List all possible file names.
$names = array();
$prefix = substr($str, 0, $bracketStartPos);
$affix = substr($str, $bracketEndPos + 1);
foreach ($exts as $ext)
{
$names[] = "{$prefix}{$ext}{$affix}";
}
return $names;
}
function expand_filenames($input)
{
$nbBrackets = substr_count($input, '(');
// Start with the last pair.
$sets = expand_bracket_pair($input);
// Now work backwards and recurse for each generated filename set.
for ($i = 0; $i < $nbBrackets; $i++)
{
foreach ($sets as $k => $set)
{
$sets = array_merge(
$sets,
expand_bracket_pair($set)
);
}
}
// Clean up.
foreach ($sets as $k => $set)
{
if (false !== strpos($set, '('))
{
unset($sets[$k]);
}
}
$sets = array_unique($sets);
sort($sets);
return $sets;
}
var_dump(expand_filenames('/(a|b)/var/(www|www2)/index.(htm|html|php|shtml)'));

Answer 4

Maybe I'm still not getting the question, but my assumption is you are running through the filesystem until you hit one of the files, in which case you could do
$files = glob("$path/index.{htm,html,php,shtml}", GLOB_BRACE);
The resulting array will contain any file matching your extensions in $path or none. If you need to include files by a specific extension order, you can foreach over the array with an ordered list of extensions, e.g.
foreach(array('htm','html','php','shtml') as $ext) {
foreach($files as $file) {
if(pathinfo($file, PATHINFO_EXTENSION) === $ext) {
// do something
}
}
}
Edit: and yes, you can have multiple curly braces in glob.

Answer 5

The answer is given, but it's a funny puzzle and i just couldn't resist
function expand_filenames2($str) {
$r = array($str);
$n = 0;
while(preg_match('~(.*?) \( ( \w+ \| [\w|]+ ) \) (.*) ~x', $r[$n++], $m)) {
foreach(explode('|', $m[2]) as $e)
$r[] = $m[1] . $e . $m[3];
}
return array_slice($r, $n - 1);
}
print_r(expand_filenames2('/(a|b)/var/(ignore)/(www|www2)/index.(htm|html|php|shtml)!'));
maybe this explains a bit why we like regexps that much ;)