That is because the php.ini in the error display, the error is written as a file, this is the result of human settings, display_errors =on just fine.
However, it is not shown that the error is safe, it is recommended to open when debugging, and then shut down when providing services.
Provide a little information to you:
Display_errors = On
PHP default is to open the error message displayed, we changed it to:
Display_errors = Off
When the error display is turned off, the PHP function error message will no longer be displayed to the user, which will prevent the attacker from knowing the physical location of the script and some other useful information, at least to the attacker's black-box detection, to some extent. These error messages may be useful to us and can be written to the specified file, so modify the following:
Log_errors = Off
Switch
Log_errors = On
and specify the file, locate the following line:
; error_log = filename
Remove the previous; note to change the filename to a specified file, such as /usr/local/apache/logs/php_error.log
Error_log =/usr/local/apache/logs/php_error.log
All errors will be written in the Php_error.log file.
Modify the php.ini to reach the masking error message