Fix syntax error in the headers_with_mbstring.phpt skip condition

[sebastka]

Hello again,

The skip condition in tests/headers_with_mbstring.phpt is a parse error, so the test can never skip. It has stayed invisible because every job in the CI matrix has ext/mbstring, so the branch never executes. The sibling file tests/headers_without_mbstring.phpt already uses the parenthesised form.

--SKIPIF--
<?php
if (!function_exists('mb_substr') || !function_exists('mb_strlen')) {
    die "skip mbstring functions not found!";
}
?>

Why it is a parse error

exit/die accept an argument only in parentheses, so die; and die("x"); are valid while die "x"; is not. That has been true for the whole range this package supports (composer.json requires >=5.2.0), through two different parser implementations.

Checked against PHP 8.5:

$ php -l tests/headers_with_mbstring.phpt   # SKIPIF section extracted
PHP Parse error:  syntax error, unexpected double-quoted string "skip mbstring functions not fo..."

$ for c in 'die "x";' 'exit "x";' 'die("x");' 'exit("x");' 'die;' 'exit;'; do
      printf '<?php %s' "$c" > t.php
      printf '%-14s -> %s\n' "$c" "$(php -l t.php 2>&1 | head -1)"
  done
die "x";       -> PHP Parse error:  syntax error, unexpected double-quoted string "x" in t.php on line 1
exit "x";      -> PHP Parse error:  syntax error, unexpected double-quoted string "x" in t.php on line 1
die("x");      -> No syntax errors detected in t.php
exit("x");     -> No syntax errors detected in t.php
die;           -> No syntax errors detected in t.php
exit;          -> No syntax errors detected in t.php

Sources

• Zend/zend_language_parser.y (PHP-5.6): the exit_expr rule
• Zend/zend_language_parser.y (master): T_EXIT ctor_arguments, ctor_arguments, argument_list
• RFC: Transform exit() from a language construct into a standard function: PHP 8.4, parsing unchanged
• PHP manual: exit(): documented syntax and the 8.4 changelog entry

Fix

-    die "skip mbstring functions not found!";
+    die("skip mbstring functions not found!");

AI use disclosure

Anthropic's Claude LLM with Opus 5 found the bug and wrote the detailed explanation.