PHP - array seudonimo while

$tx = [];

	$c = 0;

	while($r_txt = $txt->fetch_assoc()){

		$tx[$c] = $r_txt['clave'] => $r_txt['tx'];

		$c++;

	}

$tx = [];

while($r_txt = $txt->fetch_assoc()){

	$tx[] = array($r_txt['clave'] => $r_txt['tx']);

}