Lo que buscás es una "variable variable"
http://ar2.php.net/language.variables.variable
Dan un ejemplo similar
Código PHP:
// Given these variables ...
$nameTypes = array("first", "last", "company");
$name_first = "John";
$name_last = "Doe";
$name_company = "PHP.net";
// Then this loop is ...
foreach($nameTypes as $type)
print ${"name_$type"} . "\n";
// ... equivalent to this print statement.
print "$name_first\n$name_last\n$name_company\n";
En tu caso
Código PHP:
<select name="tipo" size="1" id="select">
<option
<? if (isset($tipo))
{
echo " value=\"$tipo\">${'la_tipo_$tipo'}";
}
else
{
echo " value=\"NULL\">";
}
?>
</option>
<option value="1"><? echo $la_tipo_1 ?></option>
<option value="2"><? echo $la_tipo_2 ?></option>
<option value="3"><? echo $la_tipo_3 ?></option>
<option value="4"><? echo $la_tipo_4 ?></option>
<option value="5"><? echo $la_tipo_5 ?></option>
<option value="6"><? echo $la_tipo_6 ?></option>
<option value="7"><? echo $la_tipo_7 ?></option>
<option value="8"><? echo $la_tipo_8 ?></option>
<option value="9"><? echo $la_tipo_9 ?></option>