Regex for route matching in PHP - php

Question

I am working on my mini url router in PHP. So far I've got regex for extracting variables in the url enclosed in {}(By looking at Symfony's router code) :
public function parse($pattern)
{
$matches = '';
$variables = array();
$pos = 0;
preg_match_all('#\{\w+\}#', $pattern, $matches, PREG_OFFSET_CAPTURE | PREG_SET_ORDER);
foreach ($matches as $match)
{
$varName = substr($match[0][0], 1, -1);
if(is_numeric($varName)) {
throw new Exception('Argument cannot be a number');
}
if (in_array($varName, $variables)) {
throw new \LogicException(sprintf('More then one occurrence of variable name "%s".', $varName));
}
$variables[] = $varName;
}
return ['variables' => $variables];
}
So this method extracts the vars, now I need a regex to match the pattern of the route with the url. I started learning about regexes, but I still am not that good to wrap my head around this.

Answer 1

This will work: \/hello\/{?([^\/}]+)}?
(At least it does on the examples you provided:)
/hello/{name}
/hello/Sam
Explanation
\/ is an escaped /
hello finds hello, in case you didn't realize.
{? finds a {, if there is one.
([^\/}]+) finds everything that's not a / or }
}? finds a }, if there is one.

Answer 2

For anyone that might be interested, I got it, thanks to Laurel's answer.
This is the updated version of the method it still needs some work though :
$matches = '';
$variables = array();
$pos = 0;
$reg = '#';
$nextText = '';
preg_match_all('#\{\w+\}#', $pattern, $matches, PREG_OFFSET_CAPTURE | PREG_SET_ORDER);
foreach ($matches as $match)
{
$varName = substr($match[0][0], 1, -1);
$precedingText = substr($pattern, $pos, $match[0][1] - $pos);
$pos = $match[0][1] + strlen($match[0][0]);
$nxt = $pos - strlen($pattern);
if($nxt == 0) $nxt = strlen($pattern);
$nextText = substr($pattern, $nxt);
//$precedingText = substr($precedingText, 1, -1);
$precSegments = explode('/', $precedingText);
$precSegments = array_splice($precSegments, 1);
//$temp = 5;
echo 'nxt ' . $nextText . '<><br>';
if(strlen($precedingText) > 1)
{
foreach($precSegments as $key => $value)
{
$reg .= '\/';
$reg .= $value;
}
$reg .= '{?([^\/}]+)}?';
}
else
{
$reg .= '{?([^\/}]+)}?';
}
$nextText = str_replace('/', '\/', $nextText);
if(is_numeric($varName)) {
throw new Exception('Argument cannot be a number');
}
if (in_array($varName, $variables)) {
throw new \LogicException(sprintf('More then one occurrence of variable name "%s".', $varName));
}
$variables[] = $varName;
}
if(count($matches) < 1)
{
$reg .= str_replace('/', '\/', $pattern);
}
$reg = $reg . $nextText;
$reg .= '#';
if($pattern == '/')
{
$reg = '#^[\/]+$#';
}
return ['variables' => $variables, 'regex' => $reg];