Stdlib: mb_ucfirst()/mb_lcfirst() missing on forward 8.4 profile while mb_trim family registered (ext/mbstring/mbstring.c, extends #4007)

[PurHur]

Category

Stdlib · php-src-strict · forward-profile surface

Problem

PHP 8.4 forward profile (PHP_COMPILER_PROFILE=8.4) advertises mb_trim, mb_ltrim, and mb_rtrim, but mb_ucfirst() / mb_lcfirst() remain unregistered (PHP 8.3+ mbstring). Vendor code probing function_exists('mb_ucfirst') before use will skip UTF-8 case changes even though other 8.4 mbstring helpers are present.

Builtin	function_exists VM forward 8.4 (2026-07-10)
mb_trim	true
mb_ltrim / mb_rtrim	true
mb_ucfirst / mb_lcfirst	false
mb_strtoupper	true

php-src reference

• php/php-src ext/mbstring/mbstring.c — PHP_FUNCTION(mb_ucfirst), PHP_FUNCTION(mb_lcfirst)
• php/php-src ext/mbstring/mbstring.stub.php

PHP implementation target

• ext/mbstring/mb_ucfirst.php, mb_lcfirst.php (new) + ext/mbstring/Module.php registration
• Reuse UTF-8 case logic pattern from mb_strtoupper / host mbstring delegation
• Extend forward-profile advertisement gates in lib/CompilerVersion.php alongside mb_trim
• Related umbrella: Stdlib: mb_lcfirst() / mb_ucfirst() — multibyte case change (ext/mbstring/mbstring.c parity) #4007

Repro

./script/docker-exec.sh -- bash -lc 'PHP_COMPILER_PROFILE=8.4 php bin/vm.php test/repro/maintainer_gap_mb_ucfirst_forward84_missing.php'

Done when

• Forward 8.4: function_exists('mb_ucfirst') and mb_lcfirst true; mb_ucfirst('über') → Über
• Reference profile still withholds until stable Zend gate (no phantom on 8.2)
• Compliance .phpt under test/compliance/cases/stdlib/
• docs/capabilities.md rows via script/capability-matrix.php

[PurHur]

claim: cursor-agent-lane-a — starting this run

[PurHur]

Merged via #17614

Verification (green on branch):

• PHP_COMPILER_PROFILE=8.4 php bin/vm.php test/repro/maintainer_gap_mb_ucfirst_forward84_missing.php → ok
• mb_ucfirst('über') → Über, mb_lcfirst('Über') → über
• function_exists('mb_ucfirst') / mb_lcfirst true on forward 8.4, false on reference 8.2 profile
• Compliance: mb_ucfirst_lcfirst*.phpt, unit gate/advertisement tests
• php script/bootstrap-inventory.php --check OK 4315/4315
• Spine coverage sync OK

[PurHur]

claim: PHP Compiler Ext — I/O & Crypto — fixing mb_ucfirst_lcfirst.phpt typo (mb_lcfirst → mb_ucfirst for eszett SS expansion case)

[PurHur]

Merged via #17815

Fix: mb_ucfirst_lcfirst.phpt line 10 called mb_lcfirst('ßtraße') but expected SStraße (sharp-s upper expansion belongs to mb_ucfirst). Changed to mb_ucfirst('ßtraße').

Verification:

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh
export PHP_COMPILER_PROFILE=8.4
vendor/bin/phpunit --filter mb_ucfirst
vendor/bin/phpunit --filter MbUcfirst
'

OK (4 + 4 tests)