The releases are tagged and signed in the PHP Git Repository. The following official GnuPG keys of the current PHP Release Manager can be used to verify the tags:
pub 2048R/9C0D5763 2015-06-09 [expires: 2024-06-06] Key fingerprint = 1A4E 8B72 77C4 2E53 DBA9 C7B9 BCAA 30EA 9C0D 5763 uid Anatol Belski <ab@php.net> pub 2048R/33CFC8B3 2014-01-14 [expires: 2020-01-13] Key fingerprint = 6E4F 6AB3 21FD C07F 2C33 2E3A C2BF 0BC4 33CF C8B3 uid Ferenc Kovacs <tyrael@php.net>
pub 2048R/33CFC8B3 2014-01-14 [expires: 2020-01-13] Key fingerprint = 6E4F 6AB3 21FD C07F 2C33 2E3A C2BF 0BC4 33CF C8B3 uid Ferenc Kovacs <tyrael@php.net> pub 2048R/90D90EC1 2013-07-18 [expire : 2016-07-17] Key fingerprint = 0BD7 8B5F 9750 0D45 0838 F95D FE85 7D9A 90D9 0EC1 uid Julien Pauli <jpauli@php.net>
pub 2048R/90D90EC1 2013-07-18 [expire : 2016-07-17] Key fingerprint = 0BD7 8B5F 9750 0D45 0838 F95D FE85 7D9A 90D9 0EC1 uid Julien Pauli <jpauli@php.net> pub 4096R/7267B52D 2012-03-20 [expires: 2016-03-19] Key fingerprint = 0B96 609E 270F 565C 1329 2B24 C13C 70B8 7267 B52D uid David Soria Parra <dsp@php.net>
A full list of GPG keys used for current and older releases is also available.