function getAge(dateString) {
    var today = new Date();
    var birthDate = new Date(dateString);
    var age = today.getFullYear() - birthDate.getFullYear();
    var m = today.getMonth() - birthDate.getMonth();
    if (m < 0 || (m === 0 && today.getDate() < birthDate.getDate())) {
        age--;
    }
    return age > 18;
}
console.log(getAge('1997-11-09'))

function hasGrown(year, month = 1, day = 1) {       // 默认为 1 月 1 日

    // 获得 1970 年到 1988 年这 18 年的总时间
    let age18 = new Date(1988, 0, 1).getTime(),
          now = new Date().getTime(),
          age = now - new Date(year, month - 1, day).getTime();

    return age >= age18;
}

<?php

function check_age($start_time=0)
{
    $time = time();
    
    $age = $time - strtotime($start_time);
    
    if($age >= (18*365*24*60*60) )
    {
        return true;
    }
    else
    {
        return false;
        
    }



}