问一下大家PHP字符串处理的问题, "￥3900起起",怎么处理成"￥3900起"?

$list = [
    '￥5000起',
    '￥3900起起',
    '￥2000',
    '￥999起起',
];

/**
 * It replaces the string '起起' with '起' and adds '起' to the end of the string if it's not already there
 * 
 * @param array list The array to be processed.
 * 
 * @return array The array with the modified strings.
 */
function handleUp(array $list) :array {
    foreach($list as &$item) {
        /* Replacing the string '起起' with '起'. */
        $item = str_replace('起起', '起', $item);

        /* Checking if the last character of the string is not '起' and if it is not, it adds '起' to the end of the string. */
        if(mb_substr($item, -1) != '起') {
            $item .= '起';
        }

    }
    unset($item);

    return $list;
}

var_dump(handleUp($list));Copy

$str = '￥3900';
preg_match_all('/\d+/',$str,$arr);
print_r($arr);Copy

trim($string, '起') . '起'Copy

function modifyList($list) {
    foreach ($list as &$item) {
        // 判断字符串中是否有两个起
        if (substr_count($item, '起') == 2) {
            // 使用 str_replace 函数去掉一个起
            $item = str_replace('起起', '起', $item);
        }
        // 判断字符串中是否没有起
        if (strpos($item, '起') === false) {
            // 在字符串末尾加上一个起
            $item .= '起';
        }
    }
    return $list;
}

// 测试
$list = [
    '￥5000起',
    '￥3900起起',
    '￥2000',
    '￥999起起',
];

print_r(modifyList($list));Copy

Array
(
    [0] => ￥5000起
    [1] => ￥3900起
    [2] => ￥2000起
    [3] => ￥999起
)Copy

"apple 笔记本 ￥3900起起，真便宜起起".replace(/(￥\d+)起起/, "$1起")Copy