Uncaught referenceError：$ counter is not defined

Question

我在我的JS文件中有一個函數，我想給一個名爲$ counter的PHP變量賦值。我收到一個錯誤：$計數器沒有被定義。

繼承人的PHP-代碼：

<?php 
$counter = 0; 

foreach($res as $category){      
    echo '<div class="category" onmouseover="doChangeFontWeight($counter);" onmouseout="undoChangeFontWeight($counter);">'; 
    echo '<p class="categoryDescription">'.utf8_encode($category['description']).'</p>'; 
    echo '</div>'; 

    $counter++; 
} 
?> 

的Javascript：

function doChangeFontWeight(counter) { 
"use strict"; 

document.getElementsByClassName("categoryDescription")[counter].setAttribute("style", "font-weight: 900");} 

Answer 1

'<div class="category" onmouseover="doChangeFontWeight('.$counter.');" onmouseout="undoChangeFontWeight('.$counter.');">'; 

變量不在PHP單引號內傳遞。

Answer 2

您可能想嘗試使用雙引號而不是單引號進行回顯。

echo "<div class='category' onmouseover='doChangeFontWeight($counter);' onmouseout='undoChangeFontWeight($counter);'>"; 
echo "<p class='categoryDescription'>".utf8_encode($category['description'])."</p>"; 
echo "</div>";