PHP preg_match find field value

Question

This is my example code:

$string = "teste aa=11 teste teste";
$var = "aa|bb|cc";
if (preg_match('/^'.$var.'/', $string,$matches)){
        echo "field [$matches[0]], value [$matches[1]]";

Output:

field [aa],value []

I'm trying to output like:

field [aa],value[11]

I tried several different regexes unsuccessfully. How can I get the value of aa with regex?

I'm trying to search multiple strings within a string and pick up their value to be able to change it later.

Answer 1

$string = "teste aa=11 teste teste";
$var = "aa|bb|cc";
preg_match('/^.*('.$var.')=(.*?)\s.*/', $string, $matches);
print_r($matches);

Outputs:

Array
(
    [0] => teste aa=11 teste teste
    [1] => aa
    [2] => 11
)