I was getting this error on my php script: Fatal error: Call to undefined function xdiff_file_diff() I realised that I didn't had the xdiff extension installed. When I tried to install it using the install pecl xdiff command, I got this errors (among other lines): configure: WARNING: You will need re2c 0.13.4 or later if you want to regenerate PHP configure: error: Please reinstall the libxdiff distribution Then I installed re2c and libxdiff: wget http://www.compdigitec.com/labs/files/re2c_0135_redhat.rpm wget ftp://ftp.task.gda.pl/vol/vol1/ftp.pld-linux.org/dists/2.0/PLD/i386/PLD/RPMS/libxdiff-0.7-1.i386.rpm rpm -ivh re2c_0135_redhat.rpm rpm -ivh libxdiff-0.7-1.i386 But after that I still get the same errors. PS: I've Googled a LOT and I found a couple of people with this problem but they didn't get an answer either :(