Tests fail because of missing serialization

[bix0r]

In commit abebab9 the Serializable interface was removed.
Turns out that this creates problems because we are using serialization for internal things.

Failing tests:

SolrDocument::hasChildDocuments() - Method test [tests/025.solrdocument_haschilddocuments.phpt]
SolrDocument::getChildDocumentsCount() - Method test [tests/026.solrdocument_getchilddocscount.phpt]
SolrDocument::getInputDocument() - Where document has child docs [tests/027.solrdocument_getinputdocument_children.phpt]
SolrDocument - clone [tests/028.solrdocument_clone.phpt]
SolrDocument - clone [tests/029.solrdocument_serialize.phpt]
SolrDocument::clear - Remove all fields from the document [tests/031.solrdocument_clear.phpt]
SolrDocument::fieldExists [tests/032.solrdocument_fieldexists.phpt]
SolrDocument::getField [tests/037.solrdocument_getfield.phpt]
SolrResponse - ParseMode [tests/101.solrresponse_parseMode.phpt]
SolrDocument - Response parsed as SolrDocument with child documents [tests/106.solrresponse_child_doc_response_solrdoc.phpt]
Solr - Fetch and Update nested documents [tests/160.solr_update_document_block.phpt]
SolrParams::serialize() - serialize params [tests/196.solrparams_serialize.phpt]
SolrParams::unserialize() [tests/197.solrparams_unserialize.phpt]

Example error:

---- EXPECTED OUTPUT
bool(true)
---- ACTUAL OUTPUT
Warning: Class SolrDocument has no unserializer in /tmp/pecl-search_engine-solr/tests/025.solrdocument_haschilddocuments.php on line 7

Warning: Class SolrDocument has no unserializer in /tmp/pecl-search_engine-solr/tests/025.solrdocument_haschilddocuments.php on line 7

Warning: Class SolrDocument has no unserializer in /tmp/pecl-search_engine-solr/tests/025.solrdocument_haschilddocuments.php on line 7

Warning: SolrDocument::hasChildDocuments(): Invalid Document Index 0. HashTable index does not exist. in /tmp/pecl-search_engine-solr/tests/025.solrdocument_haschilddocuments.php on line 8

Warning: SolrDocument::hasChildDocuments(): Internal Error 1008 generated from /tmp/pecl-search_engine-solr/src/php7/solr_functions_helpers.c 214 solr_fetch_document_entry. The observed error is a possible side-effect of an illegal/unsupported operation in userspace. Please check the documentation and try again later. in /tmp/pecl-search_engine-solr/tests/025.solrdocument_haschilddocuments.php on line 8

Fatal error: SolrDocument::hasChildDocuments(): Unable to fetch document entry for current object in /tmp/pecl-search_engine-solr/tests/025.solrdocument_haschilddocuments.php on line 8

I am afraid to make a release with this error even though I've been running this code for a few months on a dev machine.

[bix0r]

I think I have a possible fix brewing... I hope I will create PR soon.

I currently think that we should just add the new Serializable methods, but that is a bit problematic since they are not compatible.
See the SolrDocument::serialize() test: for current serialize format. There we see that we have a 'C' format with a string value. Because the new __serialize() requires an array, we have a mismatch.

Note that when unserializing php for the old format, php will pick the old unserialize() method instead of the new one.

Here is the idea for my fix:

• Add __serialize() and __unserialize() only for PHP-8.1
• Make __serialize() call the old serialize() and return an array like this ['xml' => $xml]
• Make __unserialize() require and extract a xml array key with the xml String, and then call the old serialize() with that xml string

By only adding the methods for 8.1+, we avoid possible problems in 7.4 and 8.0.

[bix0r]

Fixed in PR #43