Is this a bug in PHP? Running execute.php on Ubuntu with PHP 5.5.4 executes successfully, but on CentOS with same PHP version it gives Fatal error.

execute.php

<?php

// Autoloader that does not need subdirectories (because Gist does not support subdirectories).
// Same thing happens with default SPL autoloader where namespaced files are in subdirectories.
spl_autoload_register(
    function($class) {
        spl_autoload(str_replace("\\", "_", $class));
    }
);

$bar = new Some\Bar();

$foo = new Some\Foo();
$foo->bar($bar);

other_bar.php

<?php

namespace Other;

class Bar {
    public function baz() {
        echo "self: " . get_class($this) . "\n";
    }
}

some_bar.php

<?php

namespace Some;

use Other\Bar as OtherBar;

class Bar extends OtherBar {
    public function baz() {
        echo "self: " . get_class($this) . "\n";
        echo "parent: " . get_parent_class($this) . "\n";
    }
}

some_foo.php

<?php

namespace Some;

use Other\Bar;

class Foo {
    public function bar(Bar $bar) {
        $bar->baz();
    }
}

5.6.30 - actual

5.5.30，the same issue occurs when opcache is disabled and disappears when opcache is enabled.