Cannot find config.m4.

php 
# pecl install json
Cannot find config.m4.
Make sure that you run '/usr/bin/phpize' in the top level source directory of the module

ERROR: `phpize' failed

Oh...

で、こうインストールする

# cd /usr/local/src/
# tar xvfz /tmp/pear/download/json-1.2.1.tgz
# cd json-1.2.1/
# phpize
# ./configure
# make
# make install
# echo extension=json.so > /etc/php.d/json.ini