What are the reasons why PHP would echo errors, even with error_reporting(0)?

Note the caveat in the manual at http://uk.php.net/error_reporting:

Most of E_STRICT errors are evaluated at the compile time thus such errors are not reported in the file where error_reporting is enhanced to include E_STRICT errors (and vice versa).

If your underlying system is configured to report E_STRICT errors, these may be output before your code is even considered. Don't forget, error_reporting/ini_set are runtime evaluations, and anything performed in a "before-run" phase will not see their effects.

Based on your comment that your error is...

Parse error: syntax error, unexpected T_VARIABLE, expecting ',' or ';' in /usr/home/REDACTED/public_html/dev.php on line 11

Then the same general concept applies. Your code is never run, as it is syntactically invalid (you forgot a ';'). Therefore, your change of error reporting is never encountered.

Fixing this requires a change of the system level error reporting. For example, on Apache you may be able to place...

php_value error_reporting 0

in a .htaccess file to suppress them all, but this is system configuration dependent.

Pragmatically, don't write files with syntax errors :)

To prevent errors from displaying you can

  • Write in a .htaccess: php_flag display_errors 0
  • Split your code in separate modules where the main (parent) PHP file only sets the error_logging and then include() the other files.