Following problem:
A form sends data in a variable (GET) namend $astr. An SQL query is composed with this string. Works fine unless $astr starts with a little "e". Example:

$sql_statement = "SELECT sym_name, gid FROM groups WHERE sym_name LIKE '%$astr%' "."OR g_disc LIKE '%$astr%' ORDER BY sym_name";

results in ($astr = "efg"):

SELECT sym_name, gid FROM groups WHERE sym_name LIKE '9.411446e-270fg%' OR g_disc LIKE '5.503297e-270fg%' ORDER BY sym_name

That doesn't change when using (string)$astr or when I do $bstr=strval($astr) (and $bstr in the source)...