But...

function foo(int $x, int $y) {
    $a = [$x];
    $a[1] = $y;
    $a = $y;
    return $a;
}

<?php
function foo() {
    $o = new stdClass();
    $o->foo = 0;
    $i = 1;
    $c = $i < 2;
    if ($c) {
        $k = 2 * $i;
        $o->foo = $i;
        echo $o->foo;
    }
    $o->foo += 2;
    $o->foo++;
    return $o->foo;
}
PHP 7.4


compiled vars:  none
line     #* op             return  operands
  10     0  ECHO                   1
  14     1  RETURN                 4