Installation Problems right after php building
 

Installing PHP CLI binary: /root/ispconfig/php/bin/
Installing PHP CLI man page: /root/ispconfig/php/man/man1/
Installing PEAR environment: /root/ispconfig/php/lib/php/
[PEAR] Archive_Tar: 'xml' PHP extension is not installed
[PEAR] Console_Getopt: 'xml' PHP extension is not installed
[PEAR] PEAR: 'xml' PHP extension is not installed
[PEAR] HTML_Template_IT: 'xml' PHP extension is not installed
[PEAR] Net_UserAgent_Detect: 'xml' PHP extension is not installed
[PEAR] XML_RPC: 'xml' PHP extension is not installed
Installing build environment: /root/ispconfig/php/lib/php/build/
Installing header files: /root/ispconfig/php/include/php/
Installing helper programs: /root/ispconfig/php/bin/
program: phpize
program: php-config
program: phpextdist
ln: `/root/ispconfig/php/php': File exists
tar: /root/ispconfig/install_ispconfig/compile_aps/../binaries/aps.tar.gz: Cannot open: No such file or directory
tar: Error is not recoverable: exiting now
ERROR: Could not create aps.tar.gz
./compile: line 55: cd: /root/ispconfig/install_ispconfig/compile_aps: No such file or directory

Have a look here: http://www.howtoforge.com/forums/showthread.php?t=1057