In my code, I fill an array using this line in a loop : 

```
 $_SESSION['my_array'][] = $some_value;

```

After each execution of this line, I do some check (doesn't matter here for which purpose) using the `function in_array()`. However, at the first iteration it says : 

```
« in_array() expects parameter 2 to be array ».

```

How to fix this problem?