New Object Model
Debugging in PHP
Migrating from PHP 4 to PHP 5.0.x
PHP Manual

## Error Reporting

As of PHP 5 the error reporting constant `E_STRICT` is available, with the value 2048. When enabled, messages will be issued to warn you about code usage which is deprecated or which may not be future-proof.

> Note: `E_ALL` does not include `E_STRICT`, so it's not enabled by default. You must explicitly set the error reporting level to include `E_STRICT` in order to see these messages.

See Predefined Constants for more information.

New Object Model
Debugging in PHP
Migrating from PHP 4 to PHP 5.0.x
PHP Manual