$ which php
/usr/bin/php
$ ls -l /usr/bin/php
lrwxrwxrwx 1 root root 21 Jul 9 16:21 /usr/bin/php -> /etc/alternatives/php
$ ls -l /etc/alternatives/php
lrwxrwxrwx 1 root root 13 Jul 9 16:21 /etc/alternatives/php -> /usr/bin/php5
$ file /usr/bin/php5
/usr/bin/php5: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.26, BuildID[sha1]=0x39e3f1f9c4293920472b0ab8cc15cc3b1aa88f30, stripped