Fatal error: Cannot redeclare (function)

If you find PHP telling it cannot redeclare a function of yours, there are two possibilities: You’re using a name which is already being used by PHP. For example, in_array() is a standard PHP function – you cannot make your own function called in_array(). Try searching the PHP manual for the function name, and if it matches, change yours to a different name.

<?php
if ($foo > 50) {
    include("myfuncs.php");
}
if ($foo > 100) {
    include("myfuncs.php");
}
?>

http://www.hackingwithphp.com/19/12/3/common-errors