It's all about Temp Vars

Temp Var Example
<?php
function foo() {
  $a = "abc";
  return $a;
}
$b = foo();
?>
Spot the problem
<?php
function foo() {
   return 3;
}
function bar(&$arg) {
   $arg = "banana";
}
bar(foo());
?>
In PHP5 this now gives
Strict Standards: Only variables should be passed by reference in file on line 8
And here too
<?php
function & blah($arg) {
  if(strlen($arg)) {
    return $arg.'d';
  }
  else return null;
}
$foo = "abc";
$a = blah($foo);
echo $a;
?>
Output
abcd