PHP Error Levels & error_reporting

Also Known As

TL;DR

Explanation

PHP errors span multiple levels: E_ERROR (fatal, stops execution), E_WARNING (non-fatal runtime), E_NOTICE (minor runtime hints), E_DEPRECATED, E_STRICT (coding standards), E_PARSE (compile-time syntax), and the aggregate E_ALL. error_reporting = E_ALL is the correct development setting — it surfaces E_NOTICE and E_DEPRECATED issues that become real bugs. display_errors must be Off in production (log instead). set_error_handler() registers a custom handler to convert errors to exceptions or structured log entries. PHP 8.0 promotes many warnings to TypeErrors, making strict typing even more valuable.

Common Misconception

Why It Matters

Common Mistakes

• Setting error_reporting = 0 in development — hides all errors and makes debugging impossible.
• Not enabling E_DEPRECATED — deprecated function calls are silent until the version that removes them.
• Using display_errors = On in production — leaks file paths, stack traces, and database structure to users.
• Not converting errors to exceptions with set_error_handler() — errors and exceptions get handled inconsistently.

Code Examples

# php.ini — production with errors displayed:
error_reporting = E_ALL
display_errors = On   ; Never in production — use log_errors = On instead
log_errors = Off      ; Errors not logged — invisible failures

; php.ini — development: show everything
error_reporting = E_ALL
display_errors = On
log_errors = On

; php.ini — production: log, never display
error_reporting = E_ALL & ~E_DEPRECATED & ~E_STRICT
display_errors = Off
log_errors = On
error_log = /var/log/php/error.log

// PHP — set at runtime (overrides php.ini)
error_reporting(E_ALL);
set_error_handler(function(int $errno, string $errstr, string $file, int $line): bool {
    if (!(error_reporting() & $errno)) return false; // respect @ operator
    throw new \ErrorException($errstr, 0, $errno, $file, $line);
});

// Convert all errors to exceptions — makes them catchable and loggable

References

• ↗ https://www.php.net/manual/en/errorfunc.constants.php
• ↗ https://www.php.net/manual/en/function.set-error-handler.php

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