php - 通过 Javascript 和 PHP 添加数值

Question

基本上我正在尝试将值相乘。

我下面有一个 ul 正在回显一个数值:

<ul class="TCE">
<li><span>Average drink cost</span>&nbsp;&nbsp;<?php echo the_field('average_drink_price'); ?></li>
<li><span>Average drinks spenditure per night</span>&nbsp;&nbsp;<?php echo the_field('average_drinks_spenditure_per_night'); ?></li>
<li><span>Average drinks spenditure for the year</span>&nbsp;&nbsp;<!-- JAVA BIT --></li>
<li><span>Average drinks spenditure for 3 years</span>&nbsp;&nbsp; <!-- JAVA BIT --></li>
</ul>

我希望第三个 li 获取第二个 li 的值，然后将该值乘以 28。

然后我希望第四个 li 获取第三个 li 的值并将其乘以 3。

所以它有点像这样:

li-2 x 28 = li-3li-3 x 3 = li-4

这有道理吗？ li1 和 li2 的值将通过该 PHP 字段生成，对此有任何帮助吗，因为我不知道从哪里开始？

更新了 PHP 测试:

<?php
var_dump(the_field('average_drinks_spenditure_per_night')); 
$li2 = the_field('average_drinks_spenditure_per_night');
$li3 = ($li2 * 28) * 2.1;
$li4 = $li3 * 3;
?>

<ul class="TCE">
<li><span>Average drink cost</span>&nbsp;&nbsp;<?php echo the_field('average_drink_price'); ?></li>
<li><span>Average drinks spenditure per night</span>&nbsp;&nbsp;<?php echo $li2; ?></li>
<li><span>Average drinks spenditure for the year</span>&nbsp;&nbsp;<?php echo $li3;?><!-- JAVA BIT --></li>
<li><span>Average drinks spenditure for 3 years</span>&nbsp;&nbsp; <?php echo $li4;?><!-- JAVA BIT --></li>
</ul>

Answer 1

尝试

<?php 
$li2 = 1;
if(is_numeric(trim(the_field('average_drinks_spenditure_per_night'))))
 $li2 = trim(the_field('average_drinks_spenditure_per_night'));
$li3 = $li2 * 28;
$li4 = $li3 * 3;

?>

<ul class="TCE">
<li><span>Average drink cost</span>&nbsp;&nbsp;<?php echo   the_field('average_drink_price'); ?></li>
<li><span>Average drinks spenditure per night</span>&nbsp;&nbsp;<?php echo $li2; ?></li>
<li><span>Average drinks spenditure for the year</span>&nbsp;&nbsp;<?php  echo $li3;?><!-- JAVA BIT --></li>
<li><span>Average drinks spenditure for 3 years</span>&nbsp;&nbsp; <!-- JAVA BIT --></li>
</ul>