Language: "$this" / "{$this}" string interp outside object yields empty — Zend Error (Zend/zend_execute.c)

[PurHur]

Category

Language: · php-src-strict · $this in string interpolation

Problem

Interpolating $this in a double-quoted string, "{$this}", or heredoc outside object context must throw Error: Using $this when not in object context (Zend). VM yields an empty string with no error.

Bare $this as an expression and top-level (fn() => $this)() already match Zend (#10558 / #28814). This gap is string interpolation only.

Probed 2026-08-17 — host Zend PHP 8.2+ vs php bin/vm.php.

Repro	Zend 8.2+	VM (2026-08-17)
"$this" at file scope	Error: Using $this when not in object context	OK ''
"{$this}" at file scope	same Error	OK ''
heredoc {$this} at file scope	same Error	OK ''

php-src reference

• php/php-src Zend/zend_execute.c — $this fetch / object-context check
• php/php-src Zend/zend_vm_def.h — ZEND_FETCH_THIS / string interpolation compile

PHP implementation target

• lib/ compile/VM lowering for interpolated $this — raise the same Error as bare $this when no object context; no new runtime/*.c logic

Repro

./script/docker-exec.sh -- bash -lc 'php test/repro/maintainer_gap_this_outside_object_context.php'
./script/docker-exec.sh -- bash -lc 'php bin/vm.php test/repro/maintainer_gap_this_outside_object_context.php'

Done when

• VM (and JIT/AOT if in scope) throw Error: Using $this when not in object context for "$this" / "{$this}" / heredoc $this outside object context
• Compliance .phpt or unit guard under test/compliance/cases/ or test/unit/
• php-src-strict; no php-compiler-strict shortcut

[PurHur]

claim: PHP Runtime → PHP — starting this run

Implementing php-src-strict Error for $this / {$this} string interpolation outside object context in lib/ (VM/compile lowering). No new C.

[PurHur]

Merged in #31739

Verification

• php bin/vm.php test/repro/maintainer_gap_this_outside_object_context.php → Error on dq / curly / heredoc
• ./script/phpunit.sh --filter ThisInterpOutsideObjectContextVMTest → OK (1 test)

PHP-in-PHP in lib/VM.php only (no C). {main}/plain function $this now unbound; CAST_STRING/CONCAT guarded.