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PHP 8.5 adds an optional trace key to error_get_last()

Group: Cross-analyzer regressions · Category: regression · File: regressions_error_get_last_trace.php

fatal_error_backtraces is on by default. Fatal errors collected at shutdown then carry a debug_backtrace()-shaped frame list under trace. The RFC only populates the key for those fatals, so it is optional; the other four keys (type, message, file, line) stay required. A tool whose stub is still the 8.4 shape reports trace as an unknown offset (InvalidArrayOffset, "expecting file, line, message or type"). That is the miss this file measures. Access goes through ?? so an honest optional-key reading does not also have to warn about a missing offset. Source: vimeo/psalm#11975, phpstan/phpstan-src#6470. Symfony hit the sealed 8.4 shape in symfony/symfony#66145. References: - https://wiki.php.net/rfc/error_backtraces_v2 - psalm#11975 - phpstan-src#6470

Analyzer results

AnalyzerVersionResultDiagnostics
phan 6.0.10Phan 6.0.10 php-ast version 1.1.3 PHP version used to run Phan: 8.5.11 Pass 
regressions_error_get_last_trace.php:53: Invalid offset "nope" of $error of array type array{type:int,message:string,file:string,line:int} [PhanTypeInvalidDimOffset]
phpstan 2.3.1PHPStan - PHP Static Analysis Tool 2.3.1 Pass reported Lv.3+ 
regressions_error_get_last_trace.php:53: Offset 'nope' does not exist on array{type: int, message: string, file: string, line: int, trace?: list<array{function: string, line?: int, file?: string, class?: class-string, type?: '->'|'::', args?: list<mixed>, object?: object}>}. [reported-from-level=3]
With strict-rules
regressions_error_get_last_trace.php:53: Offset 'nope' does not exist on array{type: int, message: string, file: string, line: int, trace?: list<array{function: string, line?: int, file?: string, class?: class-string, type?: '->'|'::', args?: list<mixed>, object?: object}>}.
psalm 6.20.0Psalm 6.20.0@804f03c0c183d149fcd4b8c7c0c9b3fbf836d34c
next: 7.0.0-rc2		 Pass (pzoom≠) 
regressions_error_get_last_trace.php:53: Cannot access value on variable $error using offset value of 'nope', expecting 'file', 'line', 'message', 'trace' or 'type' [InvalidArrayOffset]
pzoom (Psalm port)
regressions_error_get_last_trace.php:52: Invalid array offset type: 'trace' [InvalidArrayOffset]
regressions_error_get_last_trace.php:53: Invalid array offset type: 'nope' [InvalidArrayOffset]
mago 1.57.0mago 1.57.0 Fail 
regressions_error_get_last_trace.php:52: Impossible `isset` check on key `'trace'` accessed on `array{'file': string, 'line': int, 'message': string, 'type': int}`. [impossible-nonnull-entry-check]
regressions_error_get_last_trace.php:52: Redundant null coalesce: left-hand side is always `null`. [redundant-null-coalesce]
regressions_error_get_last_trace.php:53: Undefined array key 'nope' accessed on `array{'file': string, 'line': int, 'message': string, 'type': int}`. [undefined-string-array-index]
Expectation diff
Line 52: Expected silence (quiet probe), got ["Impossible `isset` check on key `'trace'` accessed on `array{'file': string, 'line': int, 'message': string, 'type': int}`. [impossible-nonnull-entry-check]","Redundant null coalesce: left-hand side is always `null`. [redundant-null-coalesce]"]
mir 0.87.0mir 0.87.0 Pass

No diagnostics reported.

phpantom 0.11.1phpantom_lsp 0.11.1 Pass

No diagnostics reported.

intelephense 1.18.5intelephense 1.18.5 Pass

No diagnostics reported.

phpactor 2026.10.07.0Phpactor 2026.10.07.0 Pass

No diagnostics reported.

phpy 1.0.19409phpy 1.0.19409 Pass

No diagnostics reported.

qodana 262.10968.76PhpStorm 262.10968.76 Fail 
regressions_error_get_last_trace.php:52: Value should be one of: "type", "message", "file", "line" [PhpArrayKeyDoesNotMatchArrayShapeInspection]
regressions_error_get_last_trace.php:53: Value should be one of: "type", "message", "file", "line" [PhpArrayKeyDoesNotMatchArrayShapeInspection]
Expectation diff
Line 52: Expected silence (quiet probe), got ["Value should be one of: \"type\", \"message\", \"file\", \"line\" [PhpArrayKeyDoesNotMatchArrayShapeInspection]"]
noverify 0.5.5NoVerify, version 0.5.5: built on: 2025.04.22 14:36:46 OS: r-kuchinskas arm64 Commit: 4774b82f8adc53fbef38f95e97af4b953b4d1529 Pass

No diagnostics reported.

steins 0.1.8steins 0.1.8 (2026-09-21 revision 76306a9) Pass

No diagnostics reported.

phpstan-strict 2.3.1PHPStan - PHP Static Analysis Tool 2.3.1 Pass 
regressions_error_get_last_trace.php:53: Offset 'nope' does not exist on array{type: int, message: string, file: string, line: int, trace?: list<array{function: string, line?: int, file?: string, class?: class-string, type?: '->'|'::', args?: list<mixed>, object?: object}>}.
psalm-next 7.0.0-rc2Psalm 7.0.0-rc2@20339e3fe5b8d03bcd8061030eb2a83ad50e5783 Pass 
regressions_error_get_last_trace.php:53: Cannot access value on variable $error using offset value of 'nope', expecting 'file', 'line', 'message', 'trace' or 'type' [InvalidArrayOffset]

Source

<?php

declare(strict_types=1);

namespace Conformance\Tests\RegressionsErrorGetLastTrace;

/**
 * PHP 8.5 adds an optional `trace` key to `error_get_last()`.
 *
 * `fatal_error_backtraces` is on by default. Fatal errors collected at shutdown
 * then carry a `debug_backtrace()`-shaped frame list under `trace`. The RFC
 * only populates the key for those fatals, so it is optional; the other four
 * keys (`type`, `message`, `file`, `line`) stay required.
 *
 * A tool whose stub is still the 8.4 shape reports `trace` as an unknown
 * offset (`InvalidArrayOffset`, "expecting file, line, message or type"). That
 * is the miss this file measures. Access goes through `??` so an honest
 * optional-key reading does not also have to warn about a missing offset.
 *
 * Source: vimeo/psalm#11975, phpstan/phpstan-src#6470. Symfony hit the sealed
 * 8.4 shape in symfony/symfony#66145.
 *
 * References:
 * - https://wiki.php.net/rfc/error_backtraces_v2
 * - https://github.com/vimeo/psalm/pull/11975
 * - https://github.com/phpstan/phpstan-src/pull/6470
 */

function takesInt(int $value): void
{
}

function takesString(string $value): void
{
}

function takesMixed(mixed $value): void
{
}

function inspectLastError(): void
{
    $error = error_get_last();
    if ($error === null) {
        return;
    }

    takesMixed($error['type']); // V: required 8.4 key
    takesMixed($error['message']); // V
    takesMixed($error['file']); // V
    takesMixed($error['line']); // V
    takesMixed($error['trace'] ?? null); // Q: PHP 8.5 optional key — must not be an unknown offset
    takesMixed($error['nope']); // E?: unknown key — tools with an unsealed bag stay silent
}

inspectLastError();