place php errors in log file

I am running mac 10.6.4 on an iMac and am using it as a developer server.

I have Apache and Entropy php5 installed, when i write my applications, some pages wont run when php has errors, however these are not recorded on a log file, I created one php_errors.log and entered the following on the php.ini file

error_log = /usr/local/php5/logs/php_errors.log

However errors are not written to this file and i have

log_errors = true

What could be the problem