On Solaris, if upon starting Apache you get an error like this: 

Syntax error on line 33 of /usr/local/apache/conf/httpd.conf: 
Cannot load /usr/local/apache/libexec/libphp4.so into server: ld.so.1: /usr/loca 
l/apache/bin/httpd: fatal: libmysqlclient.so.10: open failed: No such file or directory 
./apachectl start: httpd could not be started 

..try inserting the following lines into the configuration section of your apachectl startup shell script: 

LD_LIBRARY_PATH=${LD_LIBRARY_PATH}:/usr/local/mysql/lib/mysql 
export LD_LIBRARY_PATH 

Change the /usr/local/mysql/ prefix to where ever your MySQL installation is. Make sure to add on the /lib/mysql extension to your own path though. 

Do your normal "apachectl start" command to start Apache and voila, no more error. Apachectl can be found in the bin directory of your Apache installation.