Description:
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I fear I can't supply a full test script but I've a reproduceable case here with PHP 7.2.7. 
I've a variable type corruption and randomized segfaults of php itself.

segfault at 7f58b9c366f7 ip 00007f58b9c366f7 sp 00007f58a03fea60 error 14 in ctype.so[7f58ba07e000+3000]
 segfault at 7f58b9c366f7 ip 00007f58b9c366f7 sp 00007f58a15fea60 error 14 in xdebug.so[7f58bb546000+40000]
segfault at 7f58b9c366f7 ip 00007f58b9c366f7 sp 00007f58a0bfea60 error 14 in xml.so[7f58baaaa000+b000]
segfault at 7f58b9c366f7 ip 00007f58b9c366f7 sp 00007f58a0bfea60 error 14 in pdo.so[7f58bacb7000+19000]

I've a function circular() which keeps a static variable that's used to store up to n (100) entries in a script that's processing coordinates.  

The function uses array_shift() to remove the oldest element from the static array when the size reaches 100.

The variable normally contains elements like this:
'2baa468ffd1672f235a35b55dbbbde80' =>
    array(6) {
      'country_name' =>
      string(13) "United States"
      'state_name' =>
      string(4) "Ohio"
      'city_name' =>
      string(10) "Youngstown"
      'zip_code' =>
      NULL
      'distance_km' =>
      double(1.7982744310941)
      'returncode' =>
      bool(true)
    }

However after running for a 102 cycles (2nd array_shift()) I'm getting a memory consumption error (256MB used, though only 100 entries are kept).
In addition the array content suddenly changes from an array into a string type.
 string(300668) "Anited States                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   "...

It works fine without array_shift()

Test script:
---------------
    public static function circular(string $identifier, string $key=NULL,$value=NULL, int $size=100)
    {
        static $storage=[];
        if ($identifier == 'GET') var_dump($storage);
        if (empty($key) && empty($value))
            return $storage[$identifier]??[];
        if (!empty($key) && empty($value))
        {
            $key=(string)md5($key);
            return $storage[$identifier][$key]??NULL;
        }
        // storage
        if (empty($key))
        {
            $storage[$identifier][]=$value;
        }
        {
            $key=(string)md5($key);
            $storage[$identifier][$key]=$value;
        }

        if (count($storage[$identifier]) > $size) $storage[$identifier] = array_shift($storage[$identifier]); // this here causes the segfaults/corruption

        return true;

    }