Hola! antes que nada gracias por la respuesta. Teniamos instalada la version 5.5, la actualizamos a la 5.6 con los mismos resultados
php -v
PHP 5.6.31-1~dotdeb+7.1 (cli) (built: Jul 10 2017 17:58:17)
Copyright (c) 1997-2016 The PHP Group
Zend Engine v2.6.0, Copyright (c) 1998-2016 Zend Technologies
with Zend OPcache v7.0.6-dev, Copyright (c) 1999-2016, by Zend Technologies
php -m
[PHP Modules]
bcmath
bz2
calendar
Core
ctype
curl
date
dba
dom
ereg
exif
fileinfo
filter
ftp
gd
gettext
hash
iconv
json
libxml
mbstring
mcrypt
mhash
openssl
pcntl
pcre
PDO
pdo_pgsql
pgsql
Phar
posix
Reflection
session
shmop
SimpleXML
soap
sockets
SPL
standard
sysvmsg
sysvsem
sysvshm
tokenizer
wddx
xml
xmlreader
xmlwriter
xsl
Zend OPcache
zip
zlib
[Zend Modules]
Zend OPcache
El server es un debian 7.11
Saludos