'; /** * 将题干中的空括号/下划线/部分异常占位符统一替换为标准空位样式。 * * @return array{0:string,1:bool} [renderedContent, replacedAnyPlaceholder] */ public static function replaceToBlankSpan(string $content, ?string $blankSpan = null, bool $collapseAdjacentBlanks = false): array { $blankSpan = $blankSpan ?: self::DEFAULT_BLANK_SPAN; $renderedContent = $content; $latexPlaceholders = []; $counter = 0; $renderedContent = preg_replace_callback('/\$(?:[^\$]|\\\\.)*\$/u', function ($matches) use (&$latexPlaceholders, &$counter, $blankSpan) { $latexContent = $matches[0]; $inner = mb_substr($latexContent, 1, mb_strlen($latexContent) - 2); // 数学环境内也可能包含填空占位符（如 $\\underline{\\qquad}$ / $\\angle A=\\underline{\\quad}$） $blankToken = '<<>>'; $innerWithBlanks = preg_replace( [ '/\\\\underline\{[^}]*\}/u', '/\\\\qquad+/u', '/\\\\quad+/u', '/[（(](?:\s| | |　)*[）)]/u', '/_{2,}/u', ], $blankToken, $inner, -1, $blankCount ); if ($blankCount > 0) { $parts = explode($blankToken, $innerWithBlanks); $rebuilt = ''; $lastIndex = count($parts) - 1; foreach ($parts as $index => $part) { if ($part !== '') { $rebuilt .= htmlspecialchars('$'.$part.'$', ENT_QUOTES | ENT_HTML5, 'UTF-8'); } if ($index < $lastIndex) { $rebuilt .= $blankSpan; } } return $rebuilt === '' ? $blankSpan : $rebuilt; } $placeholder = '<<>>'; $latexPlaceholders[$placeholder] = $latexContent; $counter++; return $placeholder; }, $renderedContent); // 兼容常见空位写法：\underline{...}、\qquad、空括号（含 nbsp 等空白）、连续下划线、尾部 \\$ $patterns = [ '/\\\underline\{[^}]*\}/u', '/\\\qquad+/u', '/[（(](?:\s| | |　)*[）)]/u', '/_{2,}/u', '/\\\\+\$(?=\s*$)/u', ]; $renderedContent = preg_replace($patterns, $blankSpan, $renderedContent); if ($collapseAdjacentBlanks) { $quotedBlankSpan = preg_quote($blankSpan, '/'); $renderedContent = preg_replace('/(?:'.$quotedBlankSpan.'(?:\s| | |　)*){2,}/u', $blankSpan, $renderedContent); } foreach ($latexPlaceholders as $placeholder => $latexContent) { if (preg_match('/^\$(.*?)(\\\\+)\$$/u', $latexContent, $match)) { $inner = rtrim($match[1]); if ($inner === '' || preg_match('/[=:：]\s*$/u', $inner)) { if ($inner === '') { $replacement = $blankSpan; } else { $replacement = htmlspecialchars('$'.$inner.'$', ENT_QUOTES | ENT_HTML5, 'UTF-8').' '.$blankSpan; } $renderedContent = str_replace($placeholder, $replacement, $renderedContent); continue; } } $encodedLatex = htmlspecialchars($latexContent, ENT_QUOTES | ENT_HTML5, 'UTF-8'); $renderedContent = str_replace($placeholder, $encodedLatex, $renderedContent); } return [$renderedContent, $renderedContent !== $content]; } public static function defaultBlankSpan(): string { return self::DEFAULT_BLANK_SPAN; } }