Assume two files. First be a.php3:

<%
  setlocale ('LC_ALL', "de_DE"); // dec. sep = ,
  $z = 3.4;
  echo $z;
%>

and second b.php3:

<%
  $z = 3.4;
  echo $z;
%>

After invocation of a.php3 the locale state is preserved
within the apache process. If the invocation of b.php3
is processed by this apache process, b.php3 yields
3,4 instead of 3.4. 

"hotfix": ensure that after each invocation of the
PHP engine the locale setting is re-set by calling
setlocale (LC_ALL, "C") or setlocale (LC_ALL, "POSIX") or
what ever is the default on the OS/machine at apache
startup.