PHP's E_ERROR signifies a critical issue where PHP cannot recover, leading to a complete halt in application execution. Causes of E_ERROR include incorrect function usage, parsing errors, calling undefined functions, and insufficient memory. To address this, developers are advised to use tools like linters and IDEs to catch syntax errors early, analyze third-party library usage, and ensure adequate memory allocation. In cases of memory issues, developers should check server limitations and other concurrent processes that might be consuming memory. While techniques like implementing a "register_shutdown_function" can handle E_ERROR gracefully, they are not recommended as they may mask underlying problems. It is crucial to address these errors promptly as they represent significant flaws in the application. Error management tools like Rollbar can assist in tracking and analyzing these issues, providing a more confident deployment experience.