Programming PHP

Example 13-5. Log-rolling error handler
function log_roller($error, $error_string) {
$file = '/var/log/php_errors.log';
if(filesize($file) > 1024) {
rename($file, $file . (string) time( ));
clearstatcache( );
}
error_log($error_string, 3, $file);
}
set_error_handler('log_roller');
for($i = 0; $i < 5000; $i++) {
trigger_error(time( ) . ": Just an error, ma'am.\n");
}
restore_error_handler( );
Generally, while you are working on a site, you will want errors shown directly in the
pages in which they occur. However, once the site goes live, it doesn’t make much
sense to show internal error messages to visitors. A common approach is to use
something like this in your php.ini file once your site goes live:
display_errors = Off
log_errors = On
error_log = /tmp/errors.log
This tells PHP to never show any errors, but instead to log them to the location specified
by the error_log directive.
Output buffering in error handlers
Using a combination of output buffering and an error handler, you can send different
content to the user, depending on whether various error conditions occur. For
example, if a script needs to connect to a database, you can suppress output of the
page until the script successfully connects to the database.
Example 13-6 shows the use of output buffering to delay output of a page until it has
been generated successfully.
Example 13-6. Output buffering to handle errors
Results!