this is for Variable scope.
A variable declared within a function has a LOCAL SCOPE and can only be accessed within that function
A variable declared outside a function has a GLOBAL SCOPE and can only be accessed outside a function:
$meinungen = Test; // is in global scope
function wpseo_set_title_callback($input) {
if (is_single()) {
return ''. $meinungen . ''. $input . ' '. $input . ''; // now $meinungen local variable which you don not assign value.
}
// return default
return $input; }
to call the value just put global with in function
function wpseo_set_title_callback($input) {
if (is_single()) {
global $meinungen;
return ''. $meinungen . ''. $input . ' '. $input . '';
}
// return default
return $input;
}