PHP字符串关键词高亮：优化重叠匹配与最佳实践

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

// 原始的迭代替换方法
foreach($keywords1 as $kw){
    if (preg_match("~\b$kw\b~i", $str1)) {
        $str1 = str_replace($kw,'<b>'.$kw.'</b>',$str1);
    }
}
foreach($keywords2 as $kw){
    if (preg_match("~\b$kw\b~i", $str2)) {
        $str2 = str_replace($kw,'<b>'.$kw.'</b>',$str2);
    }
}
echo "原始处理 str1: " . $str1; // 预期: <b>stack overflow</b>, 实际可能: <b>stack</b> overflow
echo "<br>";
echo "原始处理 str2: " . $str2; // 预期: <b>stack overflow</b>, 实际可能: <b>stack overflow</b>
?>

<?php
$str = "This is a stack overflow issue.";
$keyword = "stack";
// 使用 \b 匹配完整的词，/i 进行不区分大小写匹配
$str = preg_replace("/\b" . $keyword . "\b/i", "<b>$0</b>", $str);
echo $str; // 输出: This is a <b>stack</b> overflow issue.
?>

<?php
$str = "What's the best price? Find it here.";
$keyword = "price?"; // 包含特殊字符 '?'

// 如果不使用 preg_quote，'?' 会被解释为量词，导致错误或非预期行为
// $pattern = "/\b" . $keyword . "\b/i"; // 错误或警告
$pattern = "/\b" . preg_quote($keyword, '/') . "\b/i"; // '/' 是正则表达式分隔符
$str = preg_replace($pattern, "<b>$0</b>", $str);
echo $str; // 输出: What's the best <b>price?</b> Find it here.
?>

<?php
$str = "你好世界，这是一个PHP教程。";
$keyword = "PHP教程";

// 添加 u 修正符以支持 Unicode
$pattern = "/\b" . preg_quote($keyword, '/') . "\b/ui";
$str = preg_replace($pattern, "<b>$0</b>", $str);
echo $str; // 输出: 你好世界，这是一个<b>PHP教程</b>。
?>

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

// 步骤1: 对关键词数组进行长度降序排序
// usort 期望一个比较函数，返回负数、零或正数
usort($keywords1, function($a, $b) {
    return strlen($b) - strlen($a); // 降序排列
});
usort($keywords2, function($a, $b) {
    return strlen($b) - strlen($a); // 降序排列
});

echo "处理 str1 (排序后的关键词: " . implode(", ", $keywords1) . "): ";
foreach($keywords1 as $kw) {
    // 步骤2: 使用 preg_replace 结合 preg_quote 进行安全替换
    // 注意: 这里使用 /i 进行不区分大小写匹配，可以根据需要调整
    $pattern = "/\b" . preg_quote($kw, '/') . "\b/i";
    $str1 = preg_replace($pattern, "<b>$0</b>", $str1);
}
echo $str1 . "<br>"; // 预期输出: <b>stack overflow</b>

echo "处理 str2 (排序后的关键词: " . implode(", ", $keywords2) . "): ";
foreach($keywords2 as $kw) {
    $pattern = "/\b" . preg_quote($kw, '/') . "\b/i";
    $str2 = preg_replace($pattern, "<b>$0</b>", $str2);
}
echo $str2 . "<br>"; // 预期输出: <b>stack overflow</b>
?>