Handle null initialized shared memory

[TheLevti]

The travis ci pipeline sometimes fails randomly on the ProcessManagerTest::testLargeBatchProcessing test. As it turns out, the unserialize function raises a notice, because of an non unserializable string, which phpunit translates into an exception. ProcessManager::fork catches this exception when calling $shm->send($message, false); and replaces the result with null.

The output of this bug is then the following:

There was 1 failure:

1) Spork\ProcessManagerTest::testLargeBatchProcessing with data set #0 (10)
null does not match expected type "array".

Background

When a new shared memory is created it may be filled with null.

https://www.php.net/manual/en/function.shmop-read.php#48828

shmop_read() reads and returns the whole memory segment's data. This is not useful if you're just working with strings. If you need to read a string from shared memory, call str_from_mem() on the result of shmop_read(). Similarly when writing strings to memory (instead of binary data), null terminate your strings with str_to_nts() before passing the value on to shmop_write().

As expected shmop_read returns the whole shared memory block filled with null terminators ("\x00\x00...").

Possible Fix

Before passing the shared memory contents to unserialize, make sure to truncate everything after the first null byte. Respectively add a null byte to the end of the serialized string before passing the data to shmop_write().