Enterprise Server plug-ins are not working after installing or upgrading Enterprise Server

After installing or upgrading Enterprise Server, it can happen that Server plug-ins such as those for ImageMagick or Sips do not work anymore, even though the Health Check page shows that all is working fine.

This can occur on systems with MAMP installed.

Important: Use of MAMP/WAMP/LAMP not supported
MAMP, WAMP or LAMP are single-distribution packages for Mac OS, Windows or Linux that combine the installation of Apache, PHP, and MySQL. These make them potentially ideal for quickly setting up a new Enterprise Server environment. However, MAMP mentions in its Philosophy statement that it is such packages are meant for development purposes and are not to be used in live production environments.
The use of MAMP, WAMP or LAMP for installing an Enterprise Server environment is therefore not supported.

To resolve this, follow these steps:

Step 1. Access the following file: Applications/MAMP/Library/bin/envvars

Step 2. Comment-out the following section:

#DYLD_LIBRARY_PATH="/Applications/MAMP/Library/lib:$DYLD_LIBRARY_PATH"

#export DYLD_LIBRARY_PATH

Step 3. Add the following section:

export PATH="$PATH:/opt/local/bin"

MAMP restart

Step 4. Save the file.

Step 5. Restart MAMP.