如果其中一个字段为空，我想发出通知错误

您可以使表单的每个字段有效，并根据它们显示错误。例如

<?php 
$userError = '';
if(isset($_POST['input1']) && !empty($_POST['input1'])){
//First assign some variables to posted variables like 
$fullname = $_POST["input1"];
$email = = $_POST["input2"];
$password = = $_POST["input3"];
//CHECK FULLNAME IS EMPTY
if($fullname == "") {
echo "Please Enter your Name First";
 }else if($email == "") { //IF EMAIL IS EMPTY
$userError = "Please Enter Your Email"; 
exit();
}else if($password == "") { //IF PASSWORD IS EMPTY
$userError = "Enter your password"; 
exit();
}else { //IF ALL FORM IS FILLED
   //SOME OTHER CODE
 }
}
?>

创建一个php error变量来显示如下错误 HTML表单

<form name="formLogin" method="post" action="makeit.php">
   <!-- show errors -->
   <?php echo $userError;?>
    <div class="tclpad" style="width:90px;"><span class="std">Fullname:</span></div>
    <div class="tclpad"><input name="input1" class="std" size="65" type="text" required></div>
    <div class="clear">&nbsp;</div>
    <div class="tclpad" style="width:90px;"><span class="std">email:</span></div>
    <div class="tclpad"><input name="input2" class="std" size="65" value="" type="password" required></div>
    <div class="clear">&nbsp;</div>
    <div class="tclpad" style="width:90px;"><span class="std">Six-digit pin:</span></div>
    <div class="tclpad"><input name="input3" class="std" size="10" value="" type="password" required></div>
    <div class="clear">&nbsp;</div>

。

第一个，在你发送表单之前，你可以通过JS验证它-例如检查jquery是否有效。如果'makeit.php'和form是同一个文件，那么你可以这样做:

if(isset($_POST['field_name']) && !empty($_POST['field_name'])){
//some code here
} else {
//error msg
}

顺便说一句-检查filter_var，特别是如果你想有效的电子邮件。