php >= 7.1 array_walk_recursive corrupts array value types

array_walk_test.php

<?php

function test($mode){
    $o = [
        \PDO::ATTR_ERRMODE => \PDO::ERRMODE_EXCEPTION,
        \PDO::ATTR_DEFAULT_FETCH_MODE => \PDO::FETCH_ASSOC
    ];

    var_dump($o);
    echo is_integer($o[\PDO::ATTR_ERRMODE ]).PHP_EOL;
    echo is_integer($o[\PDO::ATTR_DEFAULT_FETCH_MODE ]).PHP_EOL;


    if($mode != 'PDO'){
        // simply by having a walk across the array seems to destroy an internal type indicator
        array_walk_recursive($o, function ($value, $key) {
            //important stuff here
        });
        // but is not visible to the user
        var_dump($o);
    }

    if($mode == 'FIX-ARRAY-BY-CHECKING'){
        // just check the value types and it gets fixed.
        echo is_integer($o[\PDO::ATTR_ERRMODE ]).PHP_EOL;
        echo is_integer($o[\PDO::ATTR_DEFAULT_FETCH_MODE ]).PHP_EOL;
        // again no visible change
        var_dump($o);
    }

    $p = new \PDO('sqlite:test.sq3', null, null, $o);
    unset($p);
}

echo '**** Test 1 ***' . PHP_EOL;
echo 'Test PDO works as expected' . PHP_EOL;
echo '**** ****** ***' . PHP_EOL . PHP_EOL;
try{
    test('PDO');
}catch(\Exception $exception){
    echo $exception->getMessage();
}

echo PHP_EOL. PHP_EOL .'**** Test 2 ***' . PHP_EOL;
echo 'Test process PDO options with array_walk_recursive' . PHP_EOL;
echo '**** ****** ***' . PHP_EOL . PHP_EOL;

try{
    test('ARRAY_WALK');
}catch(\Exception $exception){
    echo $exception->getMessage();
}

echo PHP_EOL. PHP_EOL .'**** Test 3 ***' . PHP_EOL;
echo 'Test justify internal type by checking type of array values' . PHP_EOL;
echo '**** ****** ***' . PHP_EOL . PHP_EOL;
try{
    test('FIX-ARRAY-BY-CHECKING');
}catch(\Exception $exception){
    echo $exception->getMessage();
}