Search from a form

Question

I have a form with all the districts of portugal. When I select a city I do the search through the method post, get the value city and research shows everything that exists with the city countryside. So far so good. But when the value city is equal to ALL or (all), as I can say in the query that the user wants to see all cities?

Receiving the values of the form:

$localidade=$_REQUEST['localidade'];
$genero=$_REQUEST['genero'];
$idade_1=$_REQUEST['age-min'];
$idade_2=$_REQUEST['age-max'];

Consultation:

$sql = "SELECT  u.id, u.username, u.genero, u.idade, u.local, u.descricao,   u.status,u.last_login, u.photo_p_id, p.location 

FROM user AS u 

LEFT JOIN photos AS p

ON u.photo_p_id=p.id 
WHERE local='$localidade' AND genero ='$genero' AND idade BETWEEN '$idade_1' and '$idade_2'


LIMIT 5;
";

What do you think of my solution?

Receiving the form values:

$consulta="local='$localidade' AND";
}else{$consulta="";}
$genero=$_REQUEST['genero'];
$idade_1=$_REQUEST['age-min'];
$idade_2=$_REQUEST['age-max'];

Consultation:

$sql = "SELECT  u.id, u.username, u.genero, u.idade, u.local, u.descricao,  u.status,u.last_login, u.photo_p_id, p.location 

FROM user AS u 

LEFT JOIN photos AS p

ON u.photo_p_id=p.id 
WHERE $consulta genero ='$genero' AND idade BETWEEN '$idade_1' and '$idade_2'


LIMIT 5;
";