/**
 * 首字母头像
 * @param $text
 * @return string
 */
function letter_avatar($text)
{
    $total = unpack('L', hash('adler32', $text, true))[1];
    $hue = $total % 360;
    list($r, $g, $b) = hsv2rgb($hue / 360, 0.3, 0.9);
    $bg = "rgb({$r},{$g},{$b})";
    $color = "#ffffff";
    $first = mb_strtoupper(mb_substr($text, 0, 1));
    $src = base64_encode('<svg xmlns="http://www.w3.org/2000/svg" version="1.1" height="100" width="100"><rect fill="' . $bg . '" x="0" y="0" width="100" height="100"></rect><text x="50" y="50" font-size="50" text-copy="fast" fill="' . $color . '" text-anchor="middle" text-rights="admin" alignment-baseline="central">' . $first . '</text></svg>');
    return 'data:image/svg+xml;base64,' . $src;
}
function hsv2rgb($h, $s, $v)
{
    $r = $g = $b = 0;
    $i = floor($h * 6);
    $f = $h * 6 - $i;
    $p = $v * (1 - $s);
    $q = $v * (1 - $f * $s);
    $t = $v * (1 - (1 - $f) * $s);
    switch ($i % 6) {
        case 0:
            $r = $v;
            $g = $t;
            $b = $p;
            break;
        case 1:
            $r = $q;
            $g = $v;
            $b = $p;
            break;
        case 2:
            $r = $p;
            $g = $v;
            $b = $t;
            break;
        case 3:
            $r = $p;
            $g = $q;
            $b = $v;
            break;
        case 4:
            $r = $t;
            $g = $p;
            $b = $v;
            break;
        case 5:
            $r = $v;
            $g = $p;
            $b = $q;
            break;
    }
    return [
        floor($r * 255),
        floor($g * 255),
        floor($b * 255)
    ];
}    

可生成 echo "<img src='".letter_avatar('泽泽社长')."' />";

<div class="back-to-top cd-top faa-float animated" ></div>

CSS

/*gotop*/

@media (max-width:1000px){.back-to-top{display:none!important;}}
@-webkit-keyframes wrench{0%{-webkit-transform:rotate(-12deg);transform:rotate(-12deg)}8%{-webkit-transform:rotate(12deg);transform:rotate(12deg)}10%{-webkit-transform:rotate(24deg);transform:rotate(24deg)}18%,20%{-webkit-transform:rotate(-24deg);transform:rotate(-24deg)}28%,30%{-webkit-transform:rotate(24deg);transform:rotate(24deg)}38%,40%{-webkit-transform:rotate(-24deg);transform:rotate(-24deg)}48%,50%{-webkit-transform:rotate(24deg);transform:rotate(24deg)}58%,60%{-webkit-transform:rotate(-24deg);transform:rotate(-24deg)}68%{-webkit-transform:rotate(24deg);transform:rotate(24deg)}100%,75%{-webkit-transform:rotate(0deg);transform:rotate(0deg)}}@keyframes wrench{0%{-webkit-transform:rotate(-12deg);-ms-transform:rotate(-12deg);transform:rotate(-12deg)}8%{-webkit-transform:rotate(12deg);-ms-transform:rotate(12deg);transform:rotate(12deg)}10%{-webkit-transform:rotate(24deg);-ms-transform:rotate(24deg);transform:rotate(24deg)}18%,20%{-webkit-transform:rotate(-24deg);-ms-transform:rotate(-24deg);transform:rotate(-24deg)}28%,30%{-webkit-transform:rotate(24deg);-ms-transform:rotate(24deg);transform:rotate(24deg)}38%,40%{-webkit-transform:rotate(-24deg);-ms-transform:rotate(-24deg);transform:rotate(-24deg)}48%,50%{-webkit-transform:rotate(24deg);-ms-transform:rotate(24deg);transform:rotate(24deg)}58%,60%{-webkit-transform:rotate(-24deg);-ms-transform:rotate(-24deg);transform:rotate(-24deg)}68%{-webkit-transform:rotate(24deg);-ms-transform:rotate(24deg);transform:rotate(24deg)}100%,75%{-webkit-transform:rotate(0deg);-ms-transform:rotate(0deg);transform:rotate(0deg)}}.faa-parent.animated-hover:hover>.faa-wrench,.faa-wrench.animated,.faa-wrench.animated-hover:hover{-webkit-animation:wrench 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ring{0%{-webkit-transform:rotate(-15deg);transform:rotate(-15deg)}2%{-webkit-transform:rotate(15deg);transform:rotate(15deg)}4%{-webkit-transform:rotate(-18deg);transform:rotate(-18deg)}6%{-webkit-transform:rotate(18deg);transform:rotate(18deg)}8%{-webkit-transform:rotate(-22deg);transform:rotate(-22deg)}10%{-webkit-transform:rotate(22deg);transform:rotate(22deg)}12%{-webkit-transform:rotate(-18deg);transform:rotate(-18deg)}14%{-webkit-transform:rotate(18deg);transform:rotate(18deg)}16%{-webkit-transform:rotate(-12deg);transform:rotate(-12deg)}18%{-webkit-transform:rotate(12deg);transform:rotate(12deg)}100%,20%{-webkit-transform:rotate(0deg);transform:rotate(0deg)}}@keyframes 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2s ease infinite;animation:ring 2s ease infinite;transform-origin-x:50%;transform-origin-y:0;transform-origin-z:initial}.faa-parent.animated-hover:hover>.faa-ring.faa-fast,.faa-ring.animated-hover.faa-fast:hover,.faa-ring.animated.faa-fast{-webkit-animation:ring 1s ease infinite;animation:ring 1s ease infinite}.faa-parent.animated-hover:hover>.faa-ring.faa-slow,.faa-ring.animated-hover.faa-slow:hover,.faa-ring.animated.faa-slow{-webkit-animation:ring 3s ease infinite;animation:ring 3s ease infinite}@-webkit-keyframes vertical{0%{-webkit-transform:translate(0,-3px);transform:translate(0,-3px)}4%{-webkit-transform:translate(0,3px);transform:translate(0,3px)}8%{-webkit-transform:translate(0,-3px);transform:translate(0,-3px)}12%{-webkit-transform:translate(0,3px);transform:translate(0,3px)}16%{-webkit-transform:translate(0,-3px);transform:translate(0,-3px)}20%{-webkit-transform:translate(0,3px);transform:translate(0,3px)}100%,22%{-webkit-transform:translate(0,0);transform:translate(0,0)}}@keyframes vertical{0%{-webkit-transform:translate(0,-3px);-ms-transform:translate(0,-3px);transform:translate(0,-3px)}4%{-webkit-transform:translate(0,3px);-ms-transform:translate(0,3px);transform:translate(0,3px)}8%{-webkit-transform:translate(0,-3px);-ms-transform:translate(0,-3px);transform:translate(0,-3px)}12%{-webkit-transform:translate(0,3px);-ms-transform:translate(0,3px);transform:translate(0,3px)}16%{-webkit-transform:translate(0,-3px);-ms-transform:translate(0,-3px);transform:translate(0,-3px)}20%{-webkit-transform:translate(0,3px);-ms-transform:translate(0,3px);transform:translate(0,3px)}100%,22%{-webkit-transform:translate(0,0);-ms-transform:translate(0,0);transform:translate(0,0)}}.faa-parent.animated-hover:hover>.faa-vertical,.faa-vertical.animated,.faa-vertical.animated-hover:hover{-webkit-animation:vertical 2s ease infinite;animation:vertical 2s ease 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infinite}.faa-horizontal.animated-hover.faa-fast:hover,.faa-horizontal.animated.faa-fast,.faa-parent.animated-hover:hover>.faa-horizontal.faa-fast{-webkit-animation:horizontal 1s ease infinite;animation:horizontal 1s ease infinite}.faa-horizontal.animated-hover.faa-slow:hover,.faa-horizontal.animated.faa-slow,.faa-parent.animated-hover:hover>.faa-horizontal.faa-slow{-webkit-animation:horizontal 3s ease infinite;animation:horizontal 3s ease infinite}@-webkit-keyframes flash{0%,100%,50%{opacity:1}25%,75%{opacity:0}}@keyframes flash{0%,100%,50%{opacity:1}25%,75%{opacity:0}}.faa-flash.animated,.faa-flash.animated-hover:hover,.faa-parent.animated-hover:hover>.faa-flash{-webkit-animation:flash 2s ease infinite;animation:flash 2s ease infinite}.faa-flash.animated-hover.faa-fast:hover,.faa-flash.animated.faa-fast,.faa-parent.animated-hover:hover>.faa-flash.faa-fast{-webkit-animation:flash 1s ease infinite;animation:flash 1s ease 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infinite;animation:wrench 3.7s ease infinite}@-webkit-keyframes tada{0%{-webkit-transform:scale(1);transform:scale(1)}10%,20%{-webkit-transform:scale(.9) rotate(-8deg);transform:scale(.9) rotate(-8deg)}30%,50%,70%{-webkit-transform:scale(1.3) rotate(8deg);transform:scale(1.3) rotate(8deg)}40%,60%{-webkit-transform:scale(1.3) rotate(-8deg);transform:scale(1.3) rotate(-8deg)}100%,80%{-webkit-transform:scale(1) rotate(0);transform:scale(1) rotate(0)}}@keyframes tada{0%{-webkit-transform:scale(1);-ms-transform:scale(1);transform:scale(1)}10%,20%{-webkit-transform:scale(.9) rotate(-8deg);-ms-transform:scale(.9) rotate(-8deg);transform:scale(.9) rotate(-8deg)}30%,50%,70%{-webkit-transform:scale(1.3) rotate(8deg);-ms-transform:scale(1.3) rotate(8deg);transform:scale(1.3) rotate(8deg)}40%,60%{-webkit-transform:scale(1.3) rotate(-8deg);-ms-transform:scale(1.3) rotate(-8deg);transform:scale(1.3) rotate(-8deg)}100%,80%{-webkit-transform:scale(1) rotate(0);-ms-transform:scale(1) 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passing{0%{-webkit-transform:translateX(-50%);-ms-transform:translateX(-50%);transform:translateX(-50%);opacity:0}50%{-webkit-transform:translateX(0%);-ms-transform:translateX(0%);transform:translateX(0%);opacity:1}100%{-webkit-transform:translateX(50%);-ms-transform:translateX(50%);transform:translateX(50%);opacity:0}}.faa-parent.animated-hover:hover>.faa-passing,.faa-passing.animated,.faa-passing.animated-hover:hover{-webkit-animation:passing 2s linear infinite;animation:passing 2s linear infinite}.faa-parent.animated-hover:hover>.faa-passing.faa-fast,.faa-passing.animated-hover.faa-fast:hover,.faa-passing.animated.faa-fast{-webkit-animation:passing 1s linear infinite;animation:passing 1s linear infinite}.faa-parent.animated-hover:hover>.faa-passing.faa-slow,.faa-passing.animated-hover.faa-slow:hover,.faa-passing.animated.faa-slow{-webkit-animation:passing 3s linear infinite;animation:passing 3s linear infinite}@-webkit-keyframes 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linear}.faa-burst.animated-hover.faa-slow:hover,.faa-burst.animated.faa-slow,.faa-parent.animated-hover:hover>.faa-burst.faa-slow{-webkit-animation:burst 3s infinite linear;animation:burst 3s infinite linear}@-webkit-keyframes falling{0%{-webkit-transform:translateY(-50%);transform:translateY(-50%);opacity:0}50%{-webkit-transform:translateY(0%);transform:translateY(0%);opacity:1}100%{-webkit-transform:translateY(50%);transform:translateY(50%);opacity:0}}@keyframes falling{0%{-webkit-transform:translateY(-50%);-ms-transform:translateY(-50%);transform:translateY(-50%);opacity:0}50%{-webkit-transform:translateY(0%);-ms-transform:translateY(0%);transform:translateY(0%);opacity:1}100%{-webkit-transform:translateY(50%);-ms-transform:translateY(50%);transform:translateY(50%);opacity:0}}.faa-falling.animated,.faa-falling.animated-hover:hover,.faa-parent.animated-hover:hover>.faa-falling{-webkit-animation:falling 2s linear infinite;animation:falling 2s linear infinite}.faa-falling.animated-hover.faa-fast:hover,.faa-falling.animated.faa-fast,.faa-parent.animated-hover:hover>.faa-falling.faa-fast{-webkit-animation:falling 1s linear infinite;animation:falling 1s linear infinite}.faa-falling.animated-hover.faa-slow:hover,.faa-falling.animated.faa-slow,.faa-parent.animated-hover:hover>.faa-falling.faa-slow{-webkit-animation:falling 3s linear infinite;animation:falling 3s linear infinite}
@media (min-width: 1024px){.topButton{display: none;!important}#goToTop{display: none;!important}}
.back-to-top{
    cursor: pointer;
    position: fixed;
    right: 80px;
    top: -900px;
    z-index: 2;
    width: 70px;
    height: 900px;
    background: url(./img/scroll.png);
    transition: all .5s ease-in-out;
    opacity: 1;
}

js

$(function() {
        //scroll 事件适用于所有可滚动的元素和 window 对象（浏览器窗口）。
        $(window).scroll(function() {
                var scroHei = $(window).scrollTop();//滚动的高度
                if (scroHei > 500) {
                   $('.back-to-top').css('top','-200px');
                   // $('.back-to-top').fadeIn();
                } else {                                                
                    $('.back-to-top').css('top','-999px');
                    // $('.back-to-top').fadeOut();
                }
            })
            /*点击返回顶部*/
        $('.back-to-top').click(function() {
            $('body,html').animate({
                scrollTop: 0
            }, 600);
        })
    })

function count_words_read_time () {
global $post;
   $text_num = mb_strlen(preg_replace('/\s/','',html_entity_decode(strip_tags($post->post_content))),'UTF-8');
   $read_time = ceil($text_num/400);
   $output .= '本文共' . $text_num . '个字，预计阅读时间需要' . $read_time  . '分钟。';
   return $output;
}

<?php echo count_words_read_time(); ?>

/**
* 随机标签效果
*/
function random_tag_style() {
    $defaultcolor ="margin:0.25rem;--bs-badge-padding-x:0.65em;--bs-badge-padding-y:0.35em;--bs-badge-font-size:0.75em;--bs-badge-font-weight:500;--bs-badge-color:#fff;--bs-badge-border-radius:0.575rem;display:inline-block;padding:var(--bs-badge-padding-y)var(--bs-badge-padding-x);font-size:var(--bs-badge-font-size);font-weight:var(--bs-badge-font-weight);line-height:1;color:var(--bs-badge-color);text-align:center;white-space:nowrap;vertical-align:baseline;border-radius:var(--bs-badge-border-radius);";
    $colorarr = array(
        "color:#0d6efd;background-color:rgba(13,110,253,.1);text-shadow:rgb(13,110,253) 0px 0px 0px;",
        "color:#6610f2;background-color:rgba(102,16,242,.1);text-shadow:rgb(102,16,242) 0px 0px 0px;",
        "color:#20c997;background-color:rgba(32,201,151,.1);text-shadow:rgb(32,201,151) 0px 0px 0px;",
        "color:#dc3545;background-color:rgba(220,53,69,.1);text-shadow:rgb(220,53,69) 0px 0px 0px;",
        "color:#fd7e14;background-color:rgba(253,126,20,.1);text-shadow:rgb(253,126,20) 0px 0px 0px;"
    );    
    //取消echo可恢复默认
    echo $defaultcolor.$colorarr[mt_rand(0,4)];
}
/**
* 内页文章标签
*/
function cloudtags($tags) {
    $defaultcolor ="margin:0.25rem;--bs-badge-padding-x:0.65em;--bs-badge-padding-y:0.35em;--bs-badge-font-size:0.75em;--bs-badge-font-weight:500;--bs-badge-color:#fff;--bs-badge-border-radius:0.575rem;display:inline-block;padding:var(--bs-badge-padding-y)var(--bs-badge-padding-x);font-size:var(--bs-badge-font-size);font-weight:var(--bs-badge-font-weight);line-height:1;color:var(--bs-badge-color);text-align:center;white-space:nowrap;vertical-align:baseline;border-radius:var(--bs-badge-border-radius);";
    $colorarr = array(
        "color:#0d6efd;background-color:rgba(13,110,253,.1);text-shadow:rgb(13,110,253) 0px 0px 0px;",
        "color:#6610f2;background-color:rgba(102,16,242,.1);text-shadow:rgb(102,16,242) 0px 0px 0px;",
        "color:#20c997;background-color:rgba(32,201,151,.1);text-shadow:rgb(32,201,151) 0px 0px 0px;",
        "color:#dc3545;background-color:rgba(220,53,69,.1);text-shadow:rgb(220,53,69) 0px 0px 0px;",
        "color:#fd7e14;background-color:rgba(253,126,20,.1);text-shadow:rgb(253,126,20) 0px 0px 0px;"
    );    
    $sytle = $defaultcolor.$colorarr[mt_rand(0,4)];
    if ($tags===[]){    
        echo "<a>暂无标签</a>";    
    }else{
        foreach ($tags as $value) {
            //可设置默认无style的a标签
            //echo "<a href=".$value['permalink'].">".$value['slug']."</a>";
            echo "<a href=".$value['permalink']." style=".$sytle.">".$value['slug']."</a>";                
        }        
    }
}

    public static function avatarHtml($obj, $time = false)
    {
        $email = $obj->mail;
        //$avatorSrc = Utils::getAvator($email, 65);
    $avatorSrc = Utils::getAvator($email,40);
        if ($obj->parent && $time) {
            return '<img nogallery src="' . $avatorSrc . '" class="img-40px photo img-square normal-shadow" data-placement="bottom" data-toggle="tooltip" title="' . $obj->author . '">';
        } else {
            return '<img nogallery src="' . $avatorSrc . '" class="img-40px photo img-square normal-shadow">';
        }
    }

    public static function getGravator($email, $host, $size)
    {
        $options = mget();
        $default = 'mm';
        //默认使用萝莉源
        $host = 'https://gravatar.loli.net';
        $rating = Helper::options()->commentsAvatarRating;
        $hash = md5(strtolower($email));
        $url = '/avatar/';
        //$size = '40';//自定义头像大小
        if (strlen($options->defaultAvator) > 0) {
            //已经设置默认头像
            //显示gravatar头像
            $default = $options->defaultAvator;//使用设置的头像
        }
        $avatar = $host . $url . $hash . '?s=' . $size . '&r=' . $rating . '&d=' . $default;
        return $avatar;
    }