PHP字符过滤函数去除字符串最后一个逗号(rtrim)

$str = '123,333,234,';
echo rtrim($str, ',');

<?php
$text = "\t\tThese are a few words :) ...  ";
$trimmed = rtrim($text);
// $trimmed = "\t\tThese are a few words :) ..."
$trimmed = rtrim($text, " \t.");
// $trimmed = "\t\tThese are a few words :)"
$clean = rtrim($binary, "\x00..\x1F");
// trim the ASCII control characters at the end of $binary
// (from 0 to 31 inclusive)
?>