当我尝试使用内联php访问cookie时，无论出于何种原因，我的提交都会消失。
<div id='add_form'>
<form id='form' method='post' action='reg.do.php'>
<label for='date'>Date of Charge:</label><input type='text' name='date' id='date' maxlength='10' value='<?php echo (isset($_POST['name']) ? sanitize($_POST['name']) : ''); ?>' ><br>
<label for='vendor'>Vendor:</label><input type='text' name='vendor' id='vendor' value='<?php echo (isset($_POST['vendor']) ? sanitize($_POST['vendor']) : ''); ?>' ><br>
<label for='amount'>Amount:</label><input type='text' name='amount' id='amount' value='<?php echo (isset($_POST['amount']) ? sanitize($_POST['amount']) : ''); ?>' ><br>
<label for='service'>Description of Service:</label><input type='text' name='service' id='service' value='<?php echo (isset($_POST['service']) ? sanitize($_POST['service']) : ''); ?>' ><br>
<label for='winner'>Winner:</label><input type='text' name='winner' id='winner' value='<?php echo (isset($_POST['winner']) ? sanitize($_POST['winner']) : ''); ?>' ><br>
<label for='job'>Job Number:</label><input type='text' name='job' id='job' value='<?php echo (isset($_POST['job']) ? sanitize($_POST['job']) : ''); ?>' ><br>
<input type='hidden' name='user' id='user' value='<?php echo (isset($_COOKIE['cookie_id']) ? sanitize($_COOKIE['cookie_id']) : ''); ?>' >
<input type='submit' value='Submit'>
</form>
</div>
如果我去掉了最后一个隐藏的输入字段，或者将其内部的$_COOKIE访问权限更改为$_POST，那么提交按钮就会出现。我该怎么解决这个问题？
请参阅http://php.net/manual/ro/reserved.variables.cookies.php，我认为您需要在cookie上使用htmlspecialchars函数。
是否启用了display_errors？也许您的代码中有一个错误，所以php会中断，就像内联IF条件中的未关闭）；-）
试试这个。。。
<div id='add_form'>
<form id='form' method='post' action='reg.do.php'>
<label for='date'>Date of Charge:</label><input type='text' name='date' id='date' maxlength='10' value='<?php echo (isset($_POST['name']) ? sanitize($_POST['name']) : ''); ?>' ><br>
<label for='vendor'>Vendor:</label><input type='text' name='vendor' id='vendor' value='<?php echo (isset($_POST['vendor']) ? sanitize($_POST['vendor']) : ''); ?>' ><br>
<label for='amount'>Amount:</label><input type='text' name='amount' id='amount' value='<?php echo (isset($_POST['amount']) ? sanitize($_POST['amount']) : ''); ?>' ><br>
<label for='service'>Description of Service:</label><input type='text' name='service' id='service' value='<?php echo (isset($_POST['service']) ? sanitize($_POST['service']) : ''); ?>' ><br>
<label for='winner'>Winner:</label><input type='text' name='winner' id='winner' value='<?php echo (isset($_POST['winner']) ? sanitize($_POST['winner']) : ''); ?>' ><br>
<label for='job'>Job Number:</label><input type='text' name='job' id='job' value='<?php echo (isset($_POST['job']) ? sanitize($_POST['job']) : ''); ?>' ><br>
<input type='hidden' name='user' id='user' value='<?php echo ( isset($_COOKIE['cookie_id']) ) ? sanitize($_COOKIE['cookie_id']) : ''; ?>' >
<input type='submit' value='Submit'>
</form>
</div>
顺便说一下。。。最好使用某种模板引擎，而不是内联php代码。