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好吧，所以我有一個網站，它可以遠程控制使用庫WiringPi運行的Raspberry Pi上的GPIO（通用輸入/輸出）引腳。問題是，在javascript和php代碼之間，HTTPrequest.responseText總是返回undefined。 index.php文件讀出相應引腳，並打印出自己的狀態：JavaScript到PHP通信問題
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>Raspberry Pi Home Automation</title>
</head>
<body style="background-color: black;">
<?php
// Define your username and password
$username = "[not giving you my username]";
$password = "[or password]";
if ($_POST['txtUsername'] != $username || $_POST['txtPassword'] != $password) {
?>
<h1 style="color: white">Login</h1>
<form name="form" method="post" action="<?php echo $_SERVER['PHP_SELF']; ?>">
<p style="color: white"><label for="txtUsername">Username:</label>
<br /><input type="text" title="Enter your Username" name="txtUsername" /></p>
<p style="color: white"><label for="txtpassword">Password:</label>
<br /><input type="password" title="Enter your password" name="txtPassword" /></p>
<p><input type="submit" name="Submit" value="Login" /></p>
</form>
<?php
}
else {
?>
<?php
//this php script generate the first page in function of the gpio's status
$status = array (0, 0, 0, 0, 0, 0, 0, 0);
for ($i = 0; $i < count($status); $i++) {
//set the pin's mode to output and read them
if ($i != 5){
system("gpio mode ".$i." out");
} else {
system("gpio mode ".$i." in");
}
exec ("gpio read ".$i, $status[$i], $return);
//if off
if ($status[$i][0] == 0) {
echo ("<img id='button_".$i."' src='data/img/off/off_".$i.".jpg' alt='off'/>");
}
//if on
if ($status[$i][0] == 1) {
echo ("<img id='button_".$i."' src='data/img/on/on_".$i.".jpg' alt='on'/>");
}
}
?>
<?php
}
?>
<!-- javascript -->
<script src="script.js"></script>
</body>
工作正常 - 然後theres的JavaScript，它增加了點擊動作事件監聽到所有圖像，除了5號：這是一個我想要點擊時更新Pi引腳的狀態，而不是將其寫入相反狀態（與其他狀態一樣）。
//JavaScript, use pictures as buttons, sends and receives values to/from the Rpi
//These are all the buttons
var button_0 = document.getElementById("button_0");
var button_1 = document.getElementById("button_1");
var button_2 = document.getElementById("button_2");
var button_3 = document.getElementById("button_3");
var button_4 = document.getElementById("button_4");
var button_5 = document.getElementById("button_5");
var button_6 = document.getElementById("button_6");
var button_7 = document.getElementById("button_7");
//this function sends and receives the pin's status
function change_pin (pin, status) {
//this is the http request
var request = new XMLHttpRequest();
request.open("GET" , "gpio.php?pin=" + pin + "&status=" + status);
request.send(null);
//receiving information
request.onreadystatechange = function() {
if (request.readyState == 4 && request.status == 200) {
return (request.responseText);
}
//test if fail
else if (request.readyState == 4 && request.status == 500) {
alert ("server error");
return ("fail");
}
//else
else { return ("fail"); }
}
}
//these are all the button's events, it just calls the change_pin function and updates the page in function of the return of it.
button_0.addEventListener("click", function() {
//if off
if (button_0.alt === "off") {
//use the function
var new_status = change_pin (0, 0);
if (new_status !== "fail") {
button_0.alt = "on"
button_0.src = "data/img/on/on_0.jpg";
return 0;
}
}
//if on
if (button_0.alt === "on") {
//use the function
var new_status = change_pin (0, 1);
if (new_status !== "fail") {
button_0.alt = "off"
button_0.src = "data/img/off/off_0.jpg";
return 0;
}
}
});
所有的其他事件偵聽器功能看起來是一樣的，如上圖所示，除了這一個：
button_5.addEventListener("click", function() {
var new_status = change_pin (5, 0);
if (new_status == "yes")
{
button_5.alt = "on"
button_5.src = "data/img/on/on_5.jpg";
return 0;
}
else if (new_status == "no")
{
button_5.alt = "off"
button_5.src = "data/img/off/off_5.jpg";
return 0;
}
else if (new_status == "fail"){
return 0;
} else {
alert("return fail " + new_status);
}
});
我不得不這樣做的PHP代碼返回表示狀態的字符串（即我彌補），以消除類型問題的可能性：它沒有工作。這裏是gpio.php：
<!-- This page is requested by the JavaScript, it updates the pin's status and then print it -->
<?php
//Getting and using values
if (isset ($_GET["pin"]) && isset($_GET["status"])) {
$pin = strip_tags($_GET["pin"]);
$status = strip_tags($_GET["status"]);
//Testing if values are numbers
if ((is_numeric($pin)) && (is_numeric($status)) && ($pin <= 7) && ($pin >= 0) && ($status == "0") || ($status == "1")) {
if ($pin != 5){
//set the gpio's mode to output
system("gpio mode ".$pin." out");
//set the gpio to high/low
if ($status == "0") {
$status = "1";
}
else if ($status == "1") {
$status = "0";
}
system("gpio write ".$pin." ".$status);
}
//reading pin's status
$status = array (0, 0, 0, 0, 0, 0, 0, 0);
for ($i = $pin; $i == $pin; $i++) {
exec ("gpio read ".$i, $status[$i], $return);
if ($status[$i][0] == 0) {
echo ("no");
} else if ($status[$i][0] == 1) {
echo ("yes");
} else {
echo ("fail");
}
}
}
else {
echo ("fail");
}
} //print fail if cannot use values
else {
echo ("fail");
}
?>
我甚至創造了一個多餘的for循環只運行一次，以確保變量$狀態正確返回。根據其他人對這個問題的看法，我已經窮盡了，似乎是唯一的可能性。任何批評在這一點上都是有幫助的，因爲事先要感謝（並且承認這麼多的代碼）。
任何控制檯錯誤？ PHP從位置欄而不是腳本運行時返回正確的東西嗎？ – mplungjan 2014-12-07 06:30:30
是的，接線庫實際上是開發者所說的：返回一個表示引腳狀態的整數1或0。 – jimga150 2014-12-07 20:28:31