PHP字符串关键词高亮教程：解决重叠匹配与精确替换问题

<?php
$keywords1 = array("stack","stack overflow");
$keywords2 = array("stack overflow","stack");
$str1 = "stack overflow";
$str2 = "stack overflow";

// 示例1：关键词 "stack" 优先处理
foreach($keywords1 as $kw){
    if (preg_match("~\b$kw\b~i", $str1)) {
        $str1 = str_replace($kw,'<b>'.$kw.'</b>',$str1);
    }
}
// 示例2：关键词 "stack overflow" 优先处理
foreach($keywords2 as $kw){
    if (preg_match("~\b$kw\b~i", $str2)) {
        $str2 = str_replace($kw,'<b>'.$kw.'</b>',$str2);
    }
}

echo "str1 output: " . $str1; // 预期: <b>stack overflow</b>, 实际: <b>stack</b> overflow
echo "<br>";
echo "str2 output: " . $str2; // 预期: <b>stack overflow</b>, 实际: <b>stack overflow</b>
?>

// 将匹配到的 $kw 加粗
$str = preg_replace("/\b".preg_quote($kw)."\b/i", "<b>$0</b>", $str);

usort($keywords, function($a, $b){
    return strlen($a) < strlen($b); // 按字符串长度降序排序
});

<?php
function highlightKeywords(string $text, array $keywords): string
{
    // 1. 对关键词数组按长度降序排序
    usort($keywords, function($a, $b){
        return strlen($a) < strlen($b);
    });

    // 2. 遍历排序后的关键词并进行替换
    foreach ($keywords as $kw) {
        // 使用 preg_quote 转义关键词中的特殊字符
        // 使用 \b 确保词边界匹配
        // 使用 i 进行不区分大小写匹配
        // 使用 $0 引用整个匹配到的字符串
        $text = preg_replace("/\b".preg_quote($kw, '/')."\b/i", "<b>$0</b>", $text);
    }
    return $text;
}

$keywords1 = array("stack","stack overflow");
$keywords2 = array("stack overflow","stack");
$str1 = "This is a stack overflow issue related to stack.";
$str2 = "Another stack overflow problem.";

echo "Original str1: " . $str1 . "<br>";
echo "Highlighted str1: " . highlightKeywords($str1, $keywords1);
echo "<br><br>";

echo "Original str2: " . $str2 . "<br>";
echo "Highlighted str2: " . highlightKeywords($str2, $keywords2);
echo "<br>";

// 示例：处理关键词列表顺序不同的情况
$str_example = "Learn about stack and stack overflow concepts.";
$keywords_unordered = array("stack", "stack overflow", "concept");
echo "<br>Original str_example: " . $str_example . "<br>";
echo "Highlighted str_example (unordered keywords): " . highlightKeywords($str_example, $keywords_unordered);
echo "<br>";
?>

// 匹配关键词及其前后可能的词字符，并加粗整个匹配项
// 例如，如果关键词是"stack"，且字符串是"stacking"，这可能匹配"stacking"
$text = preg_replace("/\w*?".preg_quote($kw, '/')."\w*/i", "<b>$0</b>", $text);

// 匹配包含Unicode字符的关键词，并加粗
// \p{L} 匹配任何Unicode字母
$text = preg_replace("/\p{L}*?".preg_quote($kw, '/')."\p{L}*/ui", "<b>$0</b>", $text);