1. If you don’t already have the mcrypt module (in /usr/lib), download the libmcrypt source code from sourceforge here. Then extract the downloaded file in a Terminal and move inside the created directory. (cd libmcrypt-2.5.8 in my case)

2. Execute the following lines in one command in your Terminal, if you have a 64bit version of Apache/PHP:

CFLAGS=”-arch x86_64″ \
CXXFLAGS=”-arch x86_64″ \
./configure –disable-posix-threads

(for 32 bit versions: ./configure –disable-posix-threads)

2. In your Terminal, run:

make

3. If no errors, in your Terminal run:

sudo make install

4. Download the PHP source code from PHP’s website here. Extract in a Terminal and move into the extracted directory.

5. In your Terminal, run the following lines in one command:

export MACOSX_DEPLOYMENT_TARGET=10.6 \
CFLAGS=”-arch x86_64″ \
CXXFLAGS=”-arch x86_64″

./configure –prefix=/usr/local/php5
–mandir=/usr/share/man
–infodir=/usr/share/info
–sysconfdir=/etc \
–with-config-file-path=/etc \
–with-zlib \
–with-zlib-dir=/usr \
–with-openssl \
–with-iconv=/usr \
–enable-exif \
–enable-ftp \
–enable-mbstring \
–enable-mbregex \
–with-mcrypt \
–enable-sockets \
–with-mysql=/usr/local/mysql \
–with-pdo-mysql=/usr/local/mysql \
–with-mysqli=/usr/local/mysql/bin/mysql_config \
–with-apxs2=/usr/sbin/apxs

6. Correct a bug in Makefile.

As a result of a bug in PHP 5.2.9 and 5.3.0, we’ll need to correct the file Makefile generated by the configure phase. Let’s add ‘-lresolv‘ at the end of the line that begins with ‘EXTRA_LIBS‘. Leave a space and add it like ” …   -lz -licucore -lm -lresolv to whatever is there already. Do not alter the exiting text, simply add it.

7. In your Terminal, run:

make

8. If no errors, run:

sudo make install

At this point, restart apache and check your configuration with phpinfo(). Look for mcrypt as it should appear as an enabled module.