我用一些if/else语句进行了验证。
<?php
if (isset($_POST["join"])) {
if ($userpoint < $lessonpoint) { //pt
echo "you need more points";
} //pt
else { //has enough point
if ($row['num'] > 0) { //check if user took this lesson
echo "you took this lesson before.";
} //check if user took this lesson ends
else { //then let him apply to database
//define post:
$postvalue = (int)$_POST["postvalue"];
//and check
if($postvalue == '' || $postvalue <= 0 || $postvalue > $minimumpostvalue || $postvalue == is_int($postvalue)) { //check post
echo "Error.";
} //checkpost ends.
else { //insert
$sql = "INSERT into etc... VALUES (?, ?, ?)";
if($sql){ //to another database
$artibir = "UPDATE etc.";
echo "Done.";
} // to another database
}//insert
} //let him apply
} //has enough point
} //if post isset join
?>
这个效果很好。
但我想针对这种情况回显另一条错误消息：$postvalue > $minimumpostvalue
在尝试时，我迷失在if/else语句中。无论我把新语句放在哪里，我都会出错。
所有变量都已定义。
在何处以及如何放置$postvalue > $minimumpostvalue以回显不同的错误消息？
<?php
if (isset($_POST["join"])) {
if ($userpoint < $lessonpoint) { //pt
echo "you need more points";
} //pt
else { //has enough point
if ($row['num'] > 0) { //check if user took this lesson
echo "you took this lesson before.";
} //check if user took this lesson ends
else { //then let him apply to database
//define post:
$postvalue = (int) $_POST["postvalue"];
//and check
if ($postvalue == '' || $postvalue <= 0 || $postvalue > $minimumpostvalue || $postvalue == is_int($postvalue)) { //check post
if ($postvalue > $minimumpostvalue) {
echo "Another Error.";
}
else {
echo "Error.";
}
} //checkpost ends.
else { //insert
$sql = "INSERT into etc... VALUES (?, ?, ?)";
if ($sql) { //to another database
$artibir = "UPDATE etc.";
echo "Done.";
} // to another database
} //insert
} //let him apply
} //has enough point
} //if post isset join
?>
这是另一个毫无例外的变体。
一旦$valid变为false，它将跳过下一次验证。
<?php
$valid = true;
$error = '';
if ($valid && !isset($_POST["join"])) {
$error = 'Not a join post request';
$valid = false;
}
if ($valid && ($userpoint < $lessonpoint)) {
$error = 'You need more points';
$valid = false;
}
...
if($valid) {
// Database insert; redirect
} else {
// User error feedback
}
//and check
if ($postvalue > $minimumpostvalue) { //check exception
echo "Error 1.";
} elseif ($postvalue == '' || $postvalue <= 0 || $postvalue == is_int($postvalue)) { //check the rest
echo "Error 2.";
} //checkpost ends.
这是未经测试的代码，更多的是如何避免嵌套if语句的示例。
关键是要发现尽早声明您处于错误状态的条件，并尽可能快地退出，最好是抛出异常并避免else语句。
为了简单起见，我只使用了'RunTimeException()，但我很可能会根据情况定义自己的异常。然后可以捕获异常，并根据其类型显示不同的错误页面。
/**
* @param int $postvalue
* @param int $minimumpostvalue
*/
function saveToDatabase($postvalue)
{
if ($postvalue == '' || $postvalue <= 0 || $postvalue == is_int($postvalue)) {
throw new 'RuntimeException('Error 2');
}
$sql = "INSERT into etc... VALUES (?, ?, ?)";
if ($sql) {
$artibir = "UPDATE etc.";
}
}
if (!isset($_POST["join"])) {
throw new 'RuntimeException('Not a join post request');
}
if ($userpoint < $lessonpoint) {
throw new 'RuntimeException('You need more points');
}
$userHasTakenCourse = $row['num'] > 0;
if ($userHasTakenCourse) {
throw new 'RuntimeException('User has already taken the course.');
}
$postvalue = (int) $_POST["postvalue"];
if ($postvalue > $minimumpostvalue) {
throw new 'RuntimeException('Error 1');
}
saveToDatabase($postvalue);