Prevent public display of PHP errors via htaccess:
--------------------------------------------------
# supress php errors
php_flag display_startup_errors off
php_flag display_errors off
php_flag html_errors off
php_value docref_root 0
php_value docref_ext 0
Preserve (log) your site’s PHP errors via htaccess

# enable PHP error logging:
---------------------------
php_flag log_errors on
php_value error_log /home/path/public_html/domain/PHP_errors.log
Protect your site’s PHP error log via htaccess

# prevent access to PHP error log:
---------------------------------
<Files PHP_errors.log>
Order allow,deny
Deny from all
Satisfy All
</Files>

Controlling the level of PHP error reporting
--------------------------------------------
Using htaccess, it is possible to set the level of error reporting to suit your particular needs. The general format for controlling the level of PHP errors is as follows:

# general directive for setting php error level
-----------------------------------------------
php_value error_reporting integer
There are several common values used for “integer”, including:

Complete error reporting — for complete PHP error logging, use an error-reporting integer value of "8191", which will enable logging of everything except run-time notices. 1
Zend error reporting — to record both fatal and non-fatal compile-time warnings generated by the Zend scripting engine, use an error-reporting integer value of "128".
Basic error reporting — to record run-time notices, compile-time parse errors, as well as run-time errors and warnings, use “8” for the error-reporting integer value.
Minimal error reporting — to record only fatal run-time errors, use an error-reporting integer value of “1”, which will enable logging of unrecoverable errors.

# PHP error handling for production servers

# disable display of startup errors
php_flag display_startup_errors off

# disable display of all other errors
php_flag display_errors off

# disable html markup of errors
php_flag html_errors off

# enable logging of errors
php_flag log_errors on

# disable ignoring of repeat errors
php_flag ignore_repeated_errors off

# disable ignoring of unique source errors
php_flag ignore_repeated_source off

# enable logging of php memory leaks
php_flag report_memleaks on

# preserve most recent error via php_errormsg
php_flag track_errors on

# disable formatting of error reference links
php_value docref_root 0

# disable formatting of error reference links
php_value docref_ext 0

# specify path to php error log
php_value error_log /home/path/public_html/domain/PHP_errors.log

# specify recording of all php errors
# [see footnote 3] # php_value error_reporting 999999999
php_value error_reporting -1

# disable max error string length
php_value log_errors_max_len 0

# protect error log by preventing public access
<Files /home/path/public_html/domain/PHP_errors.log>
Order allow,deny
Deny from all
Satisfy All
</Files>

Putting it all together — Development Environment
-------------------------------------------------
During project development, when public access to your project is unavailable, you may find it beneficial to catch PHP errors in real time, where moment-by-moment circumstances continue to evolve. Here is a generalized, htaccess-based PHP error-handling strategy for development environments. Place this code in your target htaccess file:

# PHP error handling for development servers
php_flag display_startup_errors on
php_flag display_errors on
php_flag html_errors on
php_flag log_errors on
php_flag ignore_repeated_errors off
php_flag ignore_repeated_source off
php_flag report_memleaks on
php_flag track_errors on
php_value docref_root 0
php_value docref_ext 0
php_value error_log /home/path/public_html/domain/PHP_errors.log
# [see footnote 3] # php_value error_reporting 999999999
php_value error_reporting -1
php_value log_errors_max_len 0

<Files /home/path/public_html/domain/PHP_errors.log>
Order allow,deny
Deny from all
Satisfy All
</Files>