Some errors are only reported when all PHP error reporting is switched on. Without the error reporting on, you get the dreaded White Screen of Death.
Check for errors behind the scenes
As an alternative between showing no errors and showing all errors, you may wish to monitor the errors being generated by your site by running
tail -f /var/log/apache2/error.log
on your server.
Change settings in your dev site
You can show all errors by adding a few lines to your local testing site's settings.php:
//Note: Do not include the opening and closing PHP tags when you copy this code
In addition, navigate to Administration→ Configuration→ Development → logging and errors and select "All messages". (This sets
$conf['error_level'] = 2; .)
Switch on strict PHP error reporting
Or you can go through your development site's php.ini file, in the php folder, and switch all error reporting on. To do this, check through your php.ini file and set error reporting to
E_ALL | E_STRICT. The documentation there is very thorough, and you may find a different setting that's better suited to your needs. Warning: as the PHP documentation states, this setting is only for development sites, not for production sites.