PHP中从URL路径提取倒数第二个段的实用方法

<?php
$url_string = "https://localhost/categories/post_12345678/a25d48aff";
$url_components = parse_url($url_string);

// 检查路径是否存在，使用Null合并运算符（PHP 7+）提供默认值
$path = $url_components['path'] ?? '';
echo "原始路径: " . $path . "\n";
// 示例输出: 原始路径: /categories/post_12345678/a25d48aff
?>

<?php
$path = "/categories/post_12345678/a25d48aff";
$cleaned_path = trim($path, '/');
echo "清理后的路径: " . $cleaned_path . "\n";
// 示例输出: 清理后的路径: categories/post_12345678/a25d48aff
?>

<?php
$cleaned_path = "categories/post_12345678/a25d48aff";
$path_segments = explode("/", $cleaned_path);
print_r($path_segments);
/*
示例输出:
Array
(
    [0] => categories
    [1] => post_12345678
    [2] => a25d48aff
)
*/
?>

<?php
$path_segments = ["categories", "post_12345678", "a25d48aff"];
$reversed_segments = array_reverse($path_segments);
echo "倒数第二个段: " . $reversed_segments[1] . "\n";
// 示例输出: 倒数第二个段: post_12345678
?>

<?php
/**
 * 从URL路径中提取倒数第二个段
 *
 * @param string $url_string 待解析的URL字符串
 * @return string|null 倒数第二个路径段，如果不存在则返回null
 */
function getSecondLastSegmentFromUrl(string $url_string): ?string
{
    // 1. 解析URL获取路径
    $url_components = parse_url($url_string);
    $path = $url_components['path'] ?? '';

    // 确保路径不为空
    if (empty($path)) {
        return null;
    }

    // 2. 清理路径字符串（移除首尾斜杠）
    $cleaned_path = trim($path, '/');

    // 3. 分割路径为数组
    $path_segments = explode("/", $cleaned_path);

    // 4. 检查路径段数量，确保至少有2个段才能提取倒数第二个
    // 例如：/item/ 只有一个段 "item"，没有倒数第二个
    if (count($path_segments) < 2) {
        return null;
    }

    // 5. 反转数组并提取倒数第二个段（即反转后的索引1）
    $reversed_segments = array_reverse($path_segments);
    return $reversed_segments[1];
}

// 示例用法
$url1 = "https://localhost/categories/post_12345678/a25d48aff";
$url2 = "https://example.com/products/item-xyz/"; // 倒数第二个是 products
$url3 = "https://example.com/single-item/"; // 只有一个段，倒数第二个不存在
$url4 = "https://example.com/"; // 没有路径

echo "URL: " . $url1 . " -> 倒数第二个段: " . getSecondLastSegmentFromUrl($url1) . "\n";
echo "URL: " . $url2 . " -> 倒数第二个段: " . getSecondLastSegmentFromUrl($url2) . "\n";
echo "URL: " . $url3 . " -> 倒数第二个段: " . (getSecondLastSegmentFromUrl($url3) ?? 'N/A') . "\n";
echo "URL: " . $url4 . " -> 倒数第二个段: " . (getSecondLastSegmentFromUrl($url4) ?? 'N/A') . "\n";

?>