What is causing this error message when using search module? I have a website using drupal 7.  It has a site search that produces and error only when I search the word "application".

This is the error: 

Fatal error: Cannot redeclare my_form() (previously declared in /home/leader40/public_html/modules/php/php.module(80) : eval()'d code:8) in /home/leader40/public_html/modules/php/php.module(80) : eval()'d code on line 257

Any ideas on how to solve this or why it's happening?
You are declaring my_form function in two places somewhere in your block / view / Node where you are using php as filter. That is causing above issue.

Since you see above issue only in search page it should be an issue with blocks that are enabled in search page or search content...

Search in your database with keywords my_form using phpmyadmin or some other tool on all tables that will give you an idea from where the php code is getting executed !