In /usr/lib/rpm/macros.d/macros.rh-php70-config (from metapackage)

%scl_package_override() %{expand:
  %{?php70___pear:%global __pear %php70___pear}
  %{?php70___pecl:%global __pecl %php70___pecl}
  %{?php70___php:%global  __php  %php70___php}
  %global pear_metadir %php70_pear_metadir
  %global pear_xmldir  %php70_pear_xmldir
  %global pecl_xmldir  %php70_pecl_xmldir
  %global php_core_api %php70_php_core_api
  %global php_zend_api %php70_php_zend_api
  %global php_pdo_api  %php70_php_pdo_api
  %global php_version  %php70_php_version
  %global php_extdir   %php70_php_extdir
  %global php_inidir   %php70_php_inidir
  %global php_incldir  %php70_php_incldir
}

This is ok.

But in /usr/lib/rpm/macros.d/macros.rh-php70-php

#
# Interface versions exposed by PHP:
# 
%php56_php_core_api 20151012-64
%php56_php_zend_api 20151012-64
%php56_php_pdo_api  20150127-64
%php56_php_version  7.0.10
%php56_php_extdir   /opt/rh/rh-php70/root/usr/lib64/php/modules
%php56_php_inidir   /etc/opt/rh/rh-php70/php.d
%php56_php_incldir  /opt/rh/rh-php70/root/usr/include/php
%php56___php        /opt/rh/rh-php70/root/usr/bin/php

This is obviously wrong, thus %php_* macro are not (or badly) defined at buildtime, thus build of additional extensions is impossible.