help with php config in debian

[Xinhao Zheng <xinhaozheng@gmail.com>]

hi all,
 I was a fresh man to debian linux.Is there anyone who  can tell me
where to find the php's config file?I install php5 with following cmd:

./configure --prefix=/usr/local/php --with-mysql=/usr/local/mysql --
with-apxs2=/usr/local/apache2
/bin/apxs2
make
make install

And,is there a cache in debian linux?I run phpinfo and it told me the
php.ini was located in /usr/local/php/lib,however,there is no such
file.Although i use cmd find / -name php.ini and then rm every php.ini
it found.the php can still work well.So my question is:

where is php config file stored?
How many config file it used?
Is debian use cache for config file?