删除for循环连接字符串输出后的最后一个字符

remove last character after concatenating string output by for loop?

$holder = '';
foreach($fields as $key){
    $holder .= $key.', ';
}
echo $holder;

我有上面的代码，它输出"a, b, c， "我想去掉c后面的逗号。我试过substr，它不起作用。任何帮助吗?

$holder = join(', ', $fields)

您可以使用implode()将所有数组元素连接在一起:

<?php
   $holder = implode(', ', $fields);
   echo $holder;
?>

可以这样使用substr

$holder = '';
foreach($fields as $key){
    $holder .= $key.', ';
}
$newholder=substr($holder, 0, -1); 
echo $newholder;