"Trailing commas in function and method calls are now allowed" means function parameters, example:
<?php
function my1() {
echo "xxxxxx\n";
}
function my2() {
echo "yyyyyy\n";
}
my1(),my2(); // PHP Parse error: syntax error
my1(,); // PHP Parse error: syntax error
my1(1,); my2(2,); // OK
?>