Referenced parameters not showing as referenced

Should there be a way to tell if the argument was referenced?

Example:

<?php
function doNothing(&$var) {
$var = 'a';
}
$first = '1';
doNothing($first);
?>

Output

Block#1
    Stmt_Function<doNothing>
    Expr_Assign
        var: Var#1<$first>
        expr: LITERAL('1')
        result: Var#2
    Expr_FuncCall
        name: LITERAL('doNothing')
        args[0]: Var#1<$first>
        result: Var#3
    Terminal_Return
        expr: LITERAL(1)

Function doNothing():
Block#1
    Expr_Param
        name: LITERAL('var')
        result: Var#1<$var>
    Expr_Assign
        var: Var#2<$var>
        expr: LITERAL('a')
        result: Var#3
    Terminal_Return
        expr: LITERAL(NULL)

No source file, test, or entry point is named. Start by reproducing the PHP example and compare the argument at the call site with the parameter and assignment in the displayed CFG. Done means the output clearly indicates whether the referenced argument was referenced.