假设没有 CSV 引用问题:

Assuming there are no CSV quoting issues:

$newStr = str_replace( ',', '<br>', $string );

在看到您的回滚后，我发现您实际上想将 , 替换为 newline 字符，例如 \r, \n 或 \r\n:

After seeing your rollback, i see that you actually want to replace the , with a newline character such as \r, \n or \r\n:

$newStr = str_replace( ',', "\n", $string );