PHP installation fails on OS X 10.11 - El Capitan

Problem

You attempt to install the PHP agent on OS X 10.11 - El Capitan, and it fails.

Install daemon ([y]es, [n]o or x to e[x]it): y

FATAL: failed to copy new daemon into place
FATAL: New Relic agent installation failed.

Please contact http://support.newrelic.com
and report the above error. We have also created a tar file with
log files and other system info that can help solve the problem.

$ sudo cp ./agent/x86_64/newrelic-20121212.so /usr/lib/php/extensions/no-debug-non-zts-20121212/
cp: /usr/lib/php/extensions/no-debug-non-zts-20121212/newrelic-20121212.so: Operation not permitted

$ sudo cp ./daemon/newrelic-daemon.x86_64 /usr/bin/newrelic-daemon
cp: /usr/bin/newrelic-daemon: Operation not permitted

Solution

If necessary, you can install the PHP agent by disabling Apple's System Integrity Protection (SIP). This is true for the newrelic-install script and for manual installations.

Follow this general procedure:

1. Boot into recovery mode.
2. Disable SIP and reboot.
3. Install the New Relic PHP agent.
4. Boot into recovery mode.
5. Re-enable SIP and reboot.

There are many articles available on the web that describe SIP and the steps for disabling, re-enabling, and checking the status.

Cause

PHP agent installation requires the daemon program to be installed in /usr/bin and the extension module in /usr/lib. However, those directories have R-X permissions, which means the daemon cannot be installed by normal means.

Apple's System Integrity Protection, SIP, prevents the modification of permissions on these directories even when logged in as root, admin, or via a sudo privileged account. This also applies in situations where the PHP bin is self-contained (for example, MAMP).