Description:
------------
With opcache.protect_memory=1 enabled, the XML-RPC extension causes a segfault on PHP 7.2 as it is modifying the recursion counter of objects it touches, without first checking if they are immutable or not.

https://github.com/php/php-src/blob/28808ca96d202e63db0c407548f4fb7d4cb46d9f/ext/xmlrpc/xmlrpc-epi-php.c#L573-L575

It was fixed for 7.3 by the general recursion check refactoring: https://github.com/php/php-src/commit/cb9d81ef4f07f82835273800b0cb3d6a67816050#diff-b55aaf035c39d54c37c0f9bcc0ece5c8

It looks like this just needs some ZEND_HASH_APPLY_PROTECTION checks for 7.2

By the way, I ran into this debugging a related issue where we're seeing the nApplyCount of the shared empty array getting incremented and staying that way (but I don't know how to reproduce that yet), poisoning it for the rest of the process lifetime. Could this code ever leave the count unbalanced? or is it "harmless" as it will always be back to 0 upon finishing?

Many thanks for looking at this, apologies for not having a test script but I don't know enough about XML-RPC to extract one.

php-xmlrpc-7.2.19-2.el7.remi.x86_64

Actual result:
--------------
#0  PHP_to_XMLRPC_worker (key=key@entry=0x0, in_val=in_val@entry=0x7ffec63de950, depth=5, depth@entry=0) at /usr/src/debug/php-7.2.19/ext/xmlrpc/xmlrpc-epi-php.c:574
#1  0x00007fd26e3958a3 in PHP_to_XMLRPC (root_val=0x7ffec63de950) at /usr/src/debug/php-7.2.19/ext/xmlrpc/xmlrpc-epi-php.c:607
#2  php_xmlrpc_callback (server=<optimized out>, xRequest=0x7fd27aa704b0, data=0x7ffec63de920) at /usr/src/debug/php-7.2.19/ext/xmlrpc/xmlrpc-epi-php.c:911
#3  0x00007fd26e395a70 in zif_xmlrpc_server_call_method (execute_data=<optimized out>, return_value=0x7fd27aa20390) at /usr/src/debug/php-7.2.19/ext/xmlrpc/xmlrpc-epi-php.c:1082
#4  0x00007fd27bdd9acb in ZEND_DO_ICALL_SPEC_RETVAL_USED_HANDLER () at /usr/src/debug/php-7.2.19/Zend/zend_vm_execute.h:617
#5  execute_ex (ex=0x7fd27aa00040) at /usr/src/debug/php-7.2.19/Zend/zend_vm_execute.h:59750
#6  0x00007fd27bddf63e in zend_execute (op_array=op_array@entry=0x7fd27aa641c0, return_value=return_value@entry=0x7fd261706988)
    at /usr/src/debug/php-7.2.19/Zend/zend_vm_execute.h:63776
#7  0x00007fd27bd2d033 in zend_execute_scripts (type=2057437840, type@entry=8, retval=0x7fd261706988, retval@entry=0x0, file_count=file_count@entry=3)
    at /usr/src/debug/php-7.2.19/Zend/zend.c:1498
#8  0x00007fd27bcc7848 in php_execute_script (primary_file=primary_file@entry=0x7ffec63e0e80) at /usr/src/debug/php-7.2.19/main/main.c:2594