How do I install the Imagick PECL extension for my PHP 5.3 application?

You can build it for PHP 5.3 using the following list of commands over SSH:

# Procedure for installing IMagick for PHP5.3 on a PHP+CGI server
# Create an install directory
mkdir ~/pecl_install
cd ~/pecl_install
# Download the last version of Imagick (as seen at http://pecl.php.net/package/imagick)
wget http://pecl.php.net/get/imagick-3.0.1.tgz
# Unpack and get inside the extracted dir
tar xzvf imagick-3.0.1.tgz
cd imagick-3.0.1
# Generate the configuration script
phpize53
# Configure for php53 and make
./configure --with-php-config=/usr/local/bin/php53-config
make
# Create a folder where the custom PHP extensions would live
mkdir ~/php53-exts
# Copy the compiled extension to the custom folder
cp modules/imagick.so ~/php53-exts/
# (Optional) Link the default server extensions inside the new folder, so they are still accessible
ln -s /usr/local/lib/php53/extensions/no-debug-non-zts-20090626/* ~/php53-exts/

# Customize the php.ini file of the desired web application, so that it loads the new extension
# MAKE SURE to replace 'htdocs' with the specific application you are enabling this for
echo "extension_dir = $HOME/php53-exts" >> ~/webapps/htdocs/php.ini
echo "extension = imagick.so" >> ~/webapps/htdocs/php.ini