The frame label is not correct when there are more than two frames

[ahocquard]

The frame label is not correct when there are more than two frames in the call stack (most of the time).

How to reproduce

<?php
    $dump = fopen('php://memory', 'rw');
    $myVariableInGlobalScope = 'scope';

    function functionLevel1() {
        $myVariableInsideAFunction1 = 'level_1';
        functionLevel2();
    }

    function functionLevel2() {
        $myVariableInsideAFunction2 = 'level_2';
        functionLevel3();
    }

    function functionLevel3() {
        global $dump;
        $myVariableInsideAFunction3 = 'level_3';

        meminfo_dump($dump);
    }

    functionLevel1();

    rewind($dump);
    $meminfoData = json_decode(stream_get_contents($dump), true);
    fclose($dump);

    $symbolNames = ['myVariableInsideAFunction1', 'myVariableInsideAFunction2', 'myVariableInsideAFunction3', 'myVariableInGlobalScope'];
    foreach($meminfoData['items'] as $item) {
        if (isset($item['symbol_name']) && in_array($item['symbol_name'], $symbolNames)) {
            echo 'Frame for '.$item['symbol_name'].': '.$item['frame']."\n";
        }
    }

The output is:

Frame for myVariableInsideAFunction3: functionLevel3()
Frame for myVariableInsideAFunction2: functionLevel1()
Frame for myVariableInsideAFunction1: <GLOBAL>
Frame for myVariableInGlobalScope: <GLOBAL>

It should be:

Frame for myVariableInsideAFunction3: functionLevel3()
Frame for myVariableInsideAFunction2: functionLevel2()
Frame for myVariableInsideAFunction1: functionLevel1()
Frame for myVariableInGlobalScope: <GLOBAL>