PHP开发需求：实现字符串匹配包装与截断展示函数

Alright, let's build this PHP function to meet your exact requirements. I'll walk through the logic with clear explanations, plus include example code to test it out.

Solution Code #

function highlightAndPreview(string $str, string $wrap, string $text): string {
    // Validate input first to avoid issues with empty values
    if (empty($str) || empty($wrap)) {
        return '';
    }

    // Escape special characters in $str and $wrap for safe regex use
    $escapedStr = preg_quote($str, '/');
    $escapedWrap = preg_quote($wrap, '/');
    $wrappedMatch = $escapedWrap . $escapedStr . $escapedWrap;

    // Wrap all occurrences of $str with the $wrap string
    $modifiedText = preg_replace("/$escapedStr/", "$wrap$str$wrap", $text);

    // Regex pattern to capture up to 2 words before, the wrapped match, and up to 2 words after
    // Includes apostrophes to handle words like "don't" or "Mary's"
    $previewPattern = "/(?:(\b[\w\']+\b\s*){0,2})($wrappedMatch)(?:(\s*\b[\w\']+\b){0,2})/";

    if (preg_match($previewPattern, $modifiedText, $matches)) {
        $preview = '';

        // Add leading ellipsis if the match isn't at the start of the text
        if (strpos($modifiedText, $matches[0]) !== 0) {
            $preview .= '...';
        }

        // Append captured context, the wrapped match, and trailing context
        $preview .= trim($matches[1] ?? '') . ' ';
        $preview .= $matches[2];
        $preview .= ' ' . trim($matches[3] ?? '');

        // Add trailing ellipsis if the match isn't at the end of the text
        $matchEndPos = strrpos($modifiedText, $matches[0]) + strlen($matches[0]);
        if ($matchEndPos !== strlen($modifiedText)) {
            $preview .= '...';
        }

        // Clean up extra spaces from context trimming
        return preg_replace('/\s+/', ' ', trim($preview));
    }

    // Return empty string if no matches are found
    return '';
}

How It Works #

Let's break down each key part:

• Input Validation: We check for empty $str or $wrap first to prevent unexpected behavior from invalid inputs.
• Safe Regex Handling: preg_quote escapes any special characters (like ., *, or |) in your search and wrap strings, so the regex works reliably even with non-alphanumeric values.
• Wrapping Matches: preg_replace replaces every instance of $str with the wrapped version (e.g., test becomes |test|).
• Preview Extraction: The regex captures up to 2 words before and after the wrapped match. We then check if the match is at the start/end of the text to decide whether to add ellipsis (...) for context.
• Cleanup: We use preg_replace to remove extra spaces that might result from trimming context parts.

Example Usage #

// Your sample values
$str = "test";
$wrap = "|";
$text = "This is a test Text";

// Run the function
echo highlightAndPreview($str, $wrap, $text);
// Output: ...is a |test| Text...

Edge Cases to Consider #

• Case Sensitivity: The current code does exact case matching (so "Test" won't match "test"). If you need case-insensitive matching, add the i modifier to the regex patterns (e.g., /pattern/i).
• Multiple Matches: This function returns a preview for the first match. If you need to show previews for all matches, modify it to use preg_match_all and loop through each match to build combined previews.
• Short Text: If the match is at the start or end of the text, no leading/trailing ellipsis will be added (e.g., if $text is "test is here", the output would be |test| is here...).

内容的提问来源于stack exchange，提问作者Milan