PHP foreach that returns keys only

Question

Theoretical question that perhaps does not make any sense but still, maybe there is a clever answer.

I want to iterate through array and get its keys and to somethin

Answer 1

loop to avoid a foreach in a while.

$a = ['1','A','B','12','ui'];

 while(true) { sleep(1);
    $b = next($a) ? current($a): reset($a);
    echo key($a) , ':' , $b , PHP_EOL;
 }