php regex - can't find the error

Question

Just one simple, specific question:
I've got the string {var1}12345{var2}, and I want to get the variable names used.

if (preg_match("/{([a-zA-Z0-9]*)}/g", $url, $matches)) {
    print_r($matches);
}

If I remove the global flag, it works, but I only get the first variable, as expected. Why isn't it working with a global flag? It works when I'm testing it with the Regex Tester

Answer 1

From PHP: preg_match:

preg_match() returns the number of times pattern matches. That will be either 0 times (no match) or 1 time because preg_match() will stop searching after the first match. preg_match_all() on the contrary will continue until it reaches the end of subject. preg_match() returns FALSE if an error occurred.

Answer 2

This should do the trick (in case you need variables in format {name}):

$url = "{var1}12345{var2}";

if (preg_match_all("/{[a-zA-Z0-9]*}/", $url, $matches)) {
    print_r($matches);
}

Answer 3

Use preg_match_all to fetch several matches:

if (preg_match_all("/{([a-zA-Z0-9]*)}/", $url, $matches)) {
    print_r($matches[1]);
}