Language: function foo($this) compiles — Zend "Cannot use $this as parameter" (Zend/zend_compile.c)

[PurHur]

Category

language · php-src-strict · parameters · compile-time fatal

Problem

php-src rejects $this as a parameter name at compile time (zend_compile_params). This compiler accepts function foo($this), methods, arrows, and by-ref function foo(&$this) — illegal programs run and print instead of aborting. VM and JIT both take the accept path.

Repro	Zend 8.2+	VM/JIT (2026-08-18 @ bf1e42be86)
function foo($this) {} echo "accepted\n";	Fatal: Cannot use $this as parameter (rc=255)	accepted (rc=0)
function foo(&$this) {}	same fatal	accepted (rc=0)
fn($this) => 1	same fatal	accepted (rc=0)
class C { function m($this) {} }	same fatal	accepted (rc=0)

Sibling of #32152 (use ($this) lexical). Silent accept is a php-src-strict miss, not an error-text nit.

php-src reference

• php/php-src Zend/zend_compile.c — zend_compile_params(); rejects $this as a parameter name (Cannot use $this as parameter)

PHP implementation target

• lib/Compiler.php param compile (zend_compile_params path next to maybeEmitOptionalBeforeRequiredParamDeprecations / assertNoThisInClosureUseVars) — when a param name is $this, emit Zend's compile fatal and abort
• Same path for JIT/AOT; no new runtime/*.c logic

Repro

./script/docker-exec.sh -- bash -lc 'php bin/vm.php test/repro/maintainer_gap_param_this.php 2>&1 | head -5'
./script/docker-exec.sh -- bash -lc 'php bin/jit.php test/repro/maintainer_gap_param_this.php 2>&1 | head -5'

Done when

• VM and JIT compile-abort with Zend substring Cannot use $this as parameter (rc≠0, no accepted output) for function / method / arrow / by-ref forms
• Compliance .phpt guard under test/compliance/cases/language/ (e.g. param_this_compile_fatal.phpt)
• php-src-strict; no php-compiler-strict shortcut

[PurHur]

claim: Worker lane B — starting this run

[PurHur]

Merged in #32194 (3493c45dda).

$this as a parameter is now a compile-time fatal matching Zend (Cannot use $this as parameter, rc=255) on VM and JIT for function / method / abstract method / arrow / by-ref / closure forms.

Verification:

• php bin/vm.php test/repro/maintainer_gap_param_this.php → PHP Fatal error: Cannot use $this as parameter VM_EXIT:255
• php bin/jit.php test/repro/maintainer_gap_param_this.php → same substring, JIT_EXIT:255
• ./script/phpunit.sh --filter ParamThis → OK (19 tests, 38 assertions)
• php script/bootstrap-inventory.php --check → OK 7589/7589

PHP path: Compiler::assertNoThisAsParameter() (lib/Compiler.php); php-src Zend/zend_compile.c zend_compile_params(). Did not run full VMTest / ci-fast.