PHP error types: E_ERROR, E_WARNING, E_NOTICE, E_DEPRECATED

Beginner5 min read·php-10-001

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Concept

PHP has two distinct error reporting systems: the traditional error system (used by the engine and some extensions) and the exception system (used by user code and increasingly by the engine). Understanding both is essential for building robust applications.

Error levels: PHP errors have numeric levels combined with the E_* constants:

E_ERROR (1): Fatal errors — script stops immediately. Cannot be caught with try/catch (but set_error_handler won't see them; register_shutdown_function can).
E_WARNING (2): Non-fatal warnings — execution continues. file_get_contents on a missing file emits E_WARNING.
E_NOTICE (8): Minor issues — using undefined variables, string-to-array index access. Often indicative of bugs.
E_DEPRECATED (8192): Functions or features that will be removed in a future version.
E_STRICT (2048): Suggestions for forward-compatibility. Merged into E_ALL in PHP 7.
E_USER_* variants: User-triggered via trigger_error().

error_reporting(E_ALL): Sets which error levels to report. In development, use E_ALL. In production, suppress E_NOTICE and E_DEPRECATED display (but log them).

ini settings that matter:

display_errors = Off in production (don't leak error details to users).
log_errors = On always (log errors server-side for debugging).
error_log = /var/log/php_errors.log or use stderr for Docker/Systemd.

Code Example

php

<?php
declare(strict_types=1);

// Error level constants
echo E_ERROR;      // 1
echo E_WARNING;    // 2
echo E_NOTICE;     // 8
echo E_DEPRECATED; // 8192
echo E_ALL;        // 32767 (all errors)

// Controlling error reporting
error_reporting(E_ALL);            // all errors (development)
error_reporting(E_ALL & ~E_NOTICE); // all except notices
error_reporting(0);                  // suppress all (never do this in development)

// trigger_error — generate user-level errors
trigger_error("Something unexpected happened", E_USER_WARNING);
trigger_error("Check this usage", E_USER_DEPRECATED);
// E_USER_ERROR would be fatal: trigger_error("Fatal!", E_USER_ERROR);

// Suppressing a specific call with @ (use sparingly — hides legitimate errors)
$result = @file_get_contents('/nonexistent'); // suppresses E_WARNING
// Better: check existence first
if (file_exists('/nonexistent')) {
    $result = file_get_contents('/nonexistent');
}

// Error log output
error_log("Something went wrong"); // writes to configured error_log file
error_log("Data: " . json_encode(['key' => 'value']));

// PHP 8.0: many functions that used to emit E_WARNING now throw Exceptions/Errors
// Example: json_decode with JSON_THROW_ON_ERROR
try {
    $data = json_decode('{invalid}', true, flags: JSON_THROW_ON_ERROR);
} catch (\JsonException $e) {
    echo "JSON error: " . $e->getMessage();
}

// checking error reporting level
$level = error_reporting();
if ($level & E_NOTICE) {
    echo "Notices are enabled\n";
}

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