Apache2 config errors on previously good setup

[gary turner <gary.kk5st@gmail.com>]

As of sometime today, my Apache2 stopped working.  It has been 
performing without issues in a small network.  There have been no recent 
changes in any configurations of Apache, PHP or MySQL.   Attempts to 
restart yield:

koko:/home/gt# apache2ctl start
apache2: Syntax error on line 185 of /etc/apache2/apache2.conf: Syntax 
error on line 1 of /etc/apache2/mods-enabled/php5.load: Cannot load 
/usr/lib/apache2/modules/libphp5.so into server: 
/usr/lib/apache2/modules/libphp5.so: undefined symbol: xmlTextReaderSetup

apache2.conf lines 184, 185 and 186:
# Include module configuration:
Include /etc/apache2/mods-enabled/*.load
Include /etc/apache2/mods-enabled/*.conf

php5.load line 1:
LoadModule php5_module /usr/lib/apache2/modules/libphp5.so

/usr/lib/apache2/modules/libphp5.so exists, but I have no clue what
": undefined symbol: xmlTextReaderSetup" means.

Any suggestions for further digging will be appreciated
--
Anyone can make a usable web site. It takes a graphic
designer to make it slow, confusing and painful to use.

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