How to run commands from Software Collections and Developer Toolset?

Issue

• After installing python27 software collection, I am still getting the older version of python on system.

  # rpm -q python27-python
  python27-python-2.7.8-16.el6.x86_64
  # python --version
  Python 2.6.6
  

• g++ compiler shows RHEL 7 compiler version even after having devtoolset-4-gcc-c++ installed.

  # g++ -v
  Using built-in specs.
  COLLECT_GCC=g++
  COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-redhat-linux/4.8.5/lto-wrapper
  Target: x86_64-redhat-linux
  Configured with: ../configure --prefix=/usr --mandir=/usr/share/man --infodir=/usr/share/info --with-bugurl=http://bugzilla.redhat.com/bugzilla --enable-bootstrap --enable-shared --enable-threads=posix --enable-checking=release --with-system-zlib --enable-__cxa_atexit --disable-libunwind-exceptions --enable-gnu-unique-object --enable-linker-build-id --with-linker-hash-style=gnu --enable-languages=c,c++,objc,obj-c++,java,fortran,ada,go,lto --enable-plugin --enable-initfini-array --disable-libgcj --with-isl=/builddir/build/BUILD/gcc-4.8.5-20150702/obj-x86_64-redhat-linux/isl-install --with-cloog=/builddir/build/BUILD/gcc-4.8.5-20150702/obj-x86_64-redhat-linux/cloog-install --enable-gnu-indirect-function --with-tune=generic --with-arch_32=x86-64 --build=x86_64-redhat-linux
  Thread model: posix
  gcc version 4.8.5 20150623 (Red Hat 4.8.5-4) (GCC) 
  

• How can I make gcc installed from Developer Toolset as default compiler? Currently I have to use the absolute path /opt/rh/devtoolset-4/root/usr/bin/gcc

• Installing PHP module named apc from php54-php-pecl-apc does not appear in the list of PHP modules.

  # php -m | grep apc
  #