Create a file called .htaccess in the root of your website and put this in it.
RewriteEngine on
Options +FollowSymlinks
RewriteBase /
RewriteRule ^(.*) search.php?search=$1 [R]
Should do the trick.
I would suggest however that you make it a bit more specific, so maybe require the user of a search directory in your url. eg instead of mysite.com/IPhone use mysite.com/search/IPhone which would work like
RewriteEngine on
Options +FollowSymlinks
RewriteBase /
RewriteRule ^search/(.*) search.php?search=$1 [R]
This makes it easier to have normal pages that arnt redirected, such as about us or a basic homepage.
As Chris says, this is not PHP but Apache that does this, and whether it works can depend on your hosting setup.