Description:
------------
Operating System: Debian GNU/Linux 8 (jessie)
Kernel: Linux 3.16.0-4-amd64
Architecture: x86-64



dpkg -l | grep php
ii  libapache2-mod-php5            5.6.24+dfsg-0+deb8u1         amd64        server-side, HTML-embedded scripting language (Apache 2 module)
ii  php5                           5.6.24+dfsg-0+deb8u1         all          server-side, HTML-embedded scripting language (metapackage)
ii  php5-cli                       5.6.24+dfsg-0+deb8u1         amd64        command-line interpreter for the php5 scripting language
ii  php5-common                    5.6.24+dfsg-0+deb8u1         amd64        Common files for packages built from the php5 source
ii  php5-curl                      5.6.24+dfsg-0+deb8u1         amd64        CURL module for php5
ii  php5-gd                        5.6.24+dfsg-0+deb8u1         amd64        GD module for php5
ii  php5-geoip                     1.1.0-2                      amd64        GeoIP module for php5
ii  php5-json                      1.3.6-1                      amd64        JSON module for php5
ii  php5-mcrypt                    5.6.24+dfsg-0+deb8u1         amd64        MCrypt module for php5
ii  php5-memcache                  3.0.8-5                      amd64        memcache extension module for PHP5
rc  php5-mysql                     5.6.23+dfsg-0+deb8u1         amd64        MySQL module for php5
ii  php5-mysqlnd                   5.6.24+dfsg-0+deb8u1         amd64        MySQL module for php5 (Native Driver)
ii  php5-readline                  5.6.24+dfsg-0+deb8u1         amd64        Readline module for php5



apachectl -V
Server version: Apache/2.4.10 (Debian)
Server built:   Jul 20 2016 06:48:18
Server's Module Magic Number: 20120211:37
Server loaded:  APR 1.5.1, APR-UTIL 1.5.4
Compiled using: APR 1.5.1, APR-UTIL 1.5.4
Architecture:   64-bit
Server MPM:     prefork
  threaded:     no
    forked:     yes (variable process count)
Server compiled with....
 -D APR_HAS_SENDFILE
 -D APR_HAS_MMAP
 -D APR_HAVE_IPV6 (IPv4-mapped addresses enabled)
 -D APR_USE_SYSVSEM_SERIALIZE
 -D APR_USE_PTHREAD_SERIALIZE
 -D SINGLE_LISTEN_UNSERIALIZED_ACCEPT
 -D APR_HAS_OTHER_CHILD
 -D AP_HAVE_RELIABLE_PIPED_LOGS
 -D DYNAMIC_MODULE_LIMIT=256
 -D HTTPD_ROOT="/etc/apache2"
 -D SUEXEC_BIN="/usr/lib/apache2/suexec"
 -D DEFAULT_PIDLOG="/var/run/apache2.pid"
 -D DEFAULT_SCOREBOARD="logs/apache_runtime_status"
 -D DEFAULT_ERRORLOG="logs/error_log"
 -D AP_TYPES_CONFIG_FILE="mime.types"
 -D SERVER_CONFIG_FILE="apache2.conf"

Test script:
---------------
<?php
interface MyInterface {
    public function toHtml();
}

abstract class MyAbstract {
    protected function _toHtml()
    {
        return '';
    }

    final public function toHtml()
    {
        return $this->_toHtml();
    }
}

class MyClass extends MyAbstract implements MyInterface {
    function _toHtml() {
        return $this->toHtml();
    }
}

$obj = new MyClass();
var_dump($obj->_toHtml());
exit;

Actual result:
--------------
apache error.log
[core:notice] [pid 3031] AH00052: child pid 3516 exit signal Segmentation fault (11)

gdb backtrace
#68242 0x00007ff342d1b110 in execute_ex () from /usr/lib/apache2/modules/libphp5.so
#68243 0x00007ff342ccc9b8 in dtrace_execute_ex () from /usr/lib/apache2/modules/libphp5.so
#68244 0x00007ff342d8d2c3 in ?? () from /usr/lib/apache2/modules/libphp5.so
#68245 0x00007ff342d1b110 in execute_ex () from /usr/lib/apache2/modules/libphp5.so
#68246 0x00007ff342ccc9b8 in dtrace_execute_ex () from /usr/lib/apache2/modules/libphp5.so
#68247 0x00007ff342d8d2c3 in ?? () from /usr/lib/apache2/modules/libphp5.so
#68248 0x00007ff342d1b110 in execute_ex () from /usr/lib/apache2/modules/libphp5.so
#68249 0x00007ff342ccc9b8 in dtrace_execute_ex () from /usr/lib/apache2/modules/libphp5.so
#68250 0x00007ff342cdf500 in zend_execute_scripts () from /usr/lib/apache2/modules/libphp5.so
#68251 0x00007ff342c7ade0 in php_execute_script () from /usr/lib/apache2/modules/libphp5.so
#68252 0x00007ff342d8e9aa in ?? () from /usr/lib/apache2/modules/libphp5.so
#68253 0x00007ff34729e2a0 in ap_run_handler ()
#68254 0x00007ff34729e7e9 in ap_invoke_handler ()
#68255 0x00007ff3472b46c2 in ap_process_async_request ()
#68256 0x00007ff3472b4860 in ap_process_request ()
#68257 0x00007ff3472b1162 in ?? ()
#68258 0x00007ff3472a7b50 in ap_run_process_connection ()
#68259 0x00007ff3436b17ba in ?? () from /usr/lib/apache2/modules/mod_mpm_prefork.so
#68260 0x00007ff3436b1a01 in ?? () from /usr/lib/apache2/modules/mod_mpm_prefork.so
#68261 0x00007ff3436b2667 in ?? () from /usr/lib/apache2/modules/mod_mpm_prefork.so
#68262 0x00007ff347283e7e in ap_run_mpm ()
#68263 0x00007ff34727d3c3 in main ()

Repeating frames till the top:
??
execute_ex
dtrace_execute_ex

Similar to #70354