1/ Quick installation Replace the ext/json tree in the php sources: tar xf php-5.#.#.tar.bz2 tar xf jsonc-1.3.#.tgz rm -rf php-5.#.#/ext/json mv jsonc-1.3.# php-5.#.#/ext/json build PHP as usual. 2/ PECL installation You need to build PHP without json extension using the --disable-json option, then build jsonc as every pecl extension: tar xf jsonc-1.3.#.tgz cd jsonc-1.3.# $PHP_DIR/bin/phpize ./configure \ --with-php-config=$PHP_DIR/bin/php-config make You can also use the --with-libjson option to use the system jsonc-c library instead of the bundled copy. 3/ TEST installation If you need to build both extensions to easily switch from one to the others, build PHP with json extension as shared using --enable-json=shared. Build the pecl jsonc extension with --with-jsonc option (the module will be renamed to jsonc.so) Both can be installed, but, only one can be enabled.