php: every file's <?php open tag counts branch +1 (ternary ? alternation matches the tag) #2541

Summary

Found by the #1096 control corpus: every PHP file records branch >= 1 from its own <?php open tag — the branch rule's bare ternary ? alternation matches the ? in the tag.

Evidence

finditer on data/php/a.php (a file with zero planted branch keywords) returns ['?']; the end-to-end scan records branch 1. All four corpus php files carry the constant +1 (main 4 = tag + if/else/switch; a/c = 1 = tag alone). Pattern tail: ...|&&|\|\||\?\?|\?.

Impact

A systematic per-file branch inflation on the entire PHP ecosystem — every file's cognitive-load/branch mass is shifted up by its open tag(s), including ?>/<?= variants.

Fix shape

Exclude tag context from the ? alternation (e.g. negative lookbehind for < and lookahead for php|=|>), or strip tags in prism before counting.

References

#1096 corpus ledger php-open-tag-counts-branch; data/php/expected_signals.json bakes the current behavior.