Retrive value from php to arduino/esp

Using Arduino Project Guidance
1

Hi there, i'm trying to make an automatic door locked using RFID and esp8266, this basically will register the Id card, and only the registered id card can open the door (servo motor).

The problem is how can i retrive a value (like 0 or 1) from php file to esp8266, so that i can say if register is 1 » servo motor rotate, else (serial print "permission negate").

Here is the code of esp8266

#include <ESP8266WebServer.h>
#include <ESP8266HTTPClient.h>
//------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------//

//----------------------------------------Include the SPI and MFRC522 libraries-------------------------------------------------------------------------------------------------------------//
//----------------------------------------Download the MFRC522 / RC522 library here: https://github.com/miguelbalboa/rfid
#include <SPI.h>
#include <MFRC522.h>
//------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------//

#define SS_PIN D2  //--> SDA / SS is connected to pinout D2
#define RST_PIN D1  //--> RST is connected to pinout D1
MFRC522 mfrc522(SS_PIN, RST_PIN);  //--> Create MFRC522 instance.

#define ON_Board_LED 2  //--> Defining an On Board LED, used for indicators when the process of connecting to a wifi router

//----------------------------------------SSID and Password of your WiFi router-------------------------------------------------------------------------------------------------------------//
const char* ssid = "Noira2";
const char* password = "12345678";
//------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------//

ESP8266WebServer server(80);  //--> Server on port 80

int readsuccess;
byte readcard[4];
char str[32] = "";
String StrUID;

//-----------------------------------------------------------------------------------------------SETUP--------------------------------------------------------------------------------------//
void setup() {
  Serial.begin(115200); //--> Initialize serial communications with the PC
  SPI.begin();      //--> Init SPI bus
  mfrc522.PCD_Init(); //--> Init MFRC522 card

  delay(500);

  WiFi.begin(ssid, password); //--> Connect to your WiFi router
  Serial.println("");

  pinMode(ON_Board_LED, OUTPUT);
  digitalWrite(ON_Board_LED, HIGH); //--> Turn off Led On Board

  //----------------------------------------Wait for connection
  Serial.print("Connecting");
  while (WiFi.status() != WL_CONNECTED) {
    Serial.print(".");
    //----------------------------------------Make the On Board Flashing LED on the process of connecting to the wifi router.
    digitalWrite(ON_Board_LED, LOW);
    delay(250);
    digitalWrite(ON_Board_LED, HIGH);
    delay(250);
  }
  digitalWrite(ON_Board_LED, HIGH); //--> Turn off the On Board LED when it is connected to the wifi router.
  //----------------------------------------If successfully connected to the wifi router, the IP Address that will be visited is displayed in the serial monitor
  Serial.println("");
  Serial.print("Successfully connected to : ");
  Serial.println(ssid);
  Serial.print("IP address: ");
  Serial.println(WiFi.localIP());

  Serial.println("Please tag a card or keychain to see the UID !");
  Serial.println("");
}
//------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------//

//-----------------------------------------------------------------------------------------------LOOP---------------------------------------------------------------------------------------//
void loop() {
  // put your main code here, to run repeatedly
  readsuccess = getid();

  if (readsuccess) {
    digitalWrite(ON_Board_LED, LOW);
    HTTPClient http;    //Declare object of class HTTPClient

    String UIDresultSend, postData;
    UIDresultSend = StrUID;

    //Post Data
    postData = "UIDresult=" + UIDresultSend;

    http.begin("http://192.168.137.1/NodeMCU-and-RFID-RC522-IoT-Projects/getUID.php");  //Specify request destination
    http.addHeader("Content-Type", "application/x-www-form-urlencoded"); //Specify content-type header

    int httpCode = http.POST(postData);   //Send the request
    String payload = http.getString();    //Get the response payload

    Serial.println(UIDresultSend);
    Serial.println(httpCode);   //Print HTTP return code
    Serial.println(payload);    //Print request response payload

    http.end();  //Close connection
    delay(1000);
    digitalWrite(ON_Board_LED, HIGH);
  }
}
//------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------//

//----------------------------------------Procedure for reading and obtaining a UID from a card or keychain---------------------------------------------------------------------------------//
int getid() {
  if (!mfrc522.PICC_IsNewCardPresent()) {
    return 0;
  }
  if (!mfrc522.PICC_ReadCardSerial()) {
    return 0;
  }


  Serial.print("THE UID OF THE SCANNED CARD IS : ");
  for (int i = 0; i < 4; i++) {
    readcard[i] = mfrc522.uid.uidByte[i]; //storing the UID of the tag in readcard
    array_to_string(readcard, 4, str);
    StrUID = str;
  }
  mfrc522.PICC_HaltA();
  return 1;
}
//------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------//

//----------------------------------------Procedure to change the result of reading an array UID into a string------------------------------------------------------------------------------//
void array_to_string(byte array[], unsigned int len, char buffer[]) {
  for (unsigned int i = 0; i < len; i++)
  {
    byte nib1 = (array[i] >> 4) & 0x0F;
    byte nib2 = (array[i] >> 0) & 0x0F;
    buffer[i * 2 + 0] = nib1  < 0xA ? '0' + nib1  : 'A' + nib1  - 0xA;
    buffer[i * 2 + 1] = nib2  < 0xA ? '0' + nib2  : 'A' + nib2  - 0xA;
  }
  buffer[len * 2] = '\0';

Next the php codes

read tag.php

<?php
	$Write="<?php $" . "UIDresult=''; " . "echo $" . "UIDresult;" . " ?>";
	file_put_contents('UIDContainer.php',$Write);
?>

<!DOCTYPE html>
<html>
	<head>
		<meta name="viewport" content="width=device-width, initial-scale=1.0">
		<meta charset="utf-8">
		<link href="css/bootstrap.min.css" rel="stylesheet">
		<script src="js/bootstrap.min.js"></script>
		<script src="jquery.min.js"></script>
		<script>
			$(document).ready(function(){
				 $("#getUID").load("UIDContainer.php");
				setInterval(function() {
					$("#getUID").load("UIDContainer.php");	
				}, 500);
			});
		</script>
		<style>
		html {
			font-family: Arial;
			display: inline-block;
			margin: 0px auto;
			text-align: center;
		}

		ul.topnav {
			list-style-type: none;
			margin: auto;
			padding: 0;
			overflow: hidden;
			background-color: #4CAF50;
			width: 70%;
		}

		ul.topnav li {float: left;}

		ul.topnav li a {
			display: block;
			color: white;
			text-align: center;
			padding: 14px 16px;
			text-decoration: none;
		}

		ul.topnav li a:hover:not(.active) {background-color: #3e8e41;}

		ul.topnav li a.active {background-color: #333;}

		ul.topnav li.right {float: right;}

		@media screen and (max-width: 600px) {
			ul.topnav li.right, 
			ul.topnav li {float: none;}
		}
		
		td.lf {
			padding-left: 15px;
			padding-top: 12px;
			padding-bottom: 12px;
		}
		</style>
		
		<title>Read Tag : NodeMCU V3 ESP8266 / ESP12E with MYSQL Database</title>
	</head>
	
	<body>
		<h2 align="center">NodeMCU V3 ESP8266 / ESP12E with MYSQL Database</h2>
		<ul class="topnav">
			<li><a href="home.php">Home</a></li>
			<li><a href="user data.php">User Data</a></li>
			<li><a href="registration.php">Registration</a></li>
			<li><a class="active" href="read tag.php">Read Tag ID</a></li>
		</ul>
		
		<br>
		
		<h3 align="center" id="blink">Please Scan Tag to Display ID or User Data</h3>
		
		<p id="getUID" hidden></p>
		
		<br>
		
		<div id="show_user_data">
			<form>
				<table  width="452" border="1" bordercolor="#10a0c5" align="center"  cellpadding="0" cellspacing="1"  bgcolor="#000" style="padding: 2px">
					<tr>
						<td  height="40" align="center"  bgcolor="#10a0c5"><font  color="#FFFFFF">
							<b>User Data</b>
							</font>
						</td>
					</tr>
					<tr>
						<td  bgcolor="#f9f9f9">
							<table width="452"  border="0" align="center" cellpadding="5"  cellspacing="0">
								<tr>
									<td width="113" align="left" class="lf">ID</td>
									<td style="font-weight:bold">:</td>
									<td align="left">--------</td>
								</tr>
								<tr bgcolor="#f2f2f2">
									<td align="left" class="lf">Name</td>
									<td style="font-weight:bold">:</td>
									<td align="left">--------</td>
								</tr>
								<tr>
									<td align="left" class="lf">Gender</td>
									<td style="font-weight:bold">:</td>
									<td align="left">--------</td>
								</tr>
								<tr bgcolor="#f2f2f2">
									<td align="left" class="lf">Email</td>
									<td style="font-weight:bold">:</td>
									<td align="left">--------</td>
								</tr>
								<tr>
									<td align="left" class="lf">Mobile Number</td>
									<td style="font-weight:bold">:</td>
									<td align="left">--------</td>
								</tr>
							</table>
						</td>
					</tr>
				</table>
			</form>
		</div>

		<script>
			var myVar = setInterval(myTimer, 1000);
			var myVar1 = setInterval(myTimer1, 1000);
			var oldID="";
			clearInterval(myVar1);

			function myTimer() {
				var getID=document.getElementById("getUID").innerHTML;
				oldID=getID;
				if(getID!="") {
					myVar1 = setInterval(myTimer1, 500);
					showUser(getID);
					clearInterval(myVar);
				}
			}
			
			function myTimer1() {
				var getID=document.getElementById("getUID").innerHTML;
				if(oldID!=getID) {
					myVar = setInterval(myTimer, 500);
					clearInterval(myVar1);
				}
			}
			
			function showUser(str) {
				if (str == "") {
					document.getElementById("show_user_data").innerHTML = "";
					return;
				} else {
					if (window.XMLHttpRequest) {
						// code for IE7+, Firefox, Chrome, Opera, Safari
						xmlhttp = new XMLHttpRequest();
					} else {
						// code for IE6, IE5
						xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
					}
					xmlhttp.onreadystatechange = function() {
						if (this.readyState == 4 && this.status == 200) {
							document.getElementById("show_user_data").innerHTML = this.responseText;
						}
					};
					xmlhttp.open("GET","read tag user data.php?id="+str,true);
					xmlhttp.send();
				}
			}
			
			var blink = document.getElementById('blink');
			setInterval(function() {
				blink.style.opacity = (blink.style.opacity == 0 ? 1 : 0);
			}, 750); 
		</script>
	</body>
</html>

getUID.php

<?php
	$UIDresult=$_POST["UIDresult"];
	$Write="<?php $" . "UIDresult='" . $UIDresult . "'; " . "echo $" . "UIDresult;" . " ?>";
	file_put_contents('UIDContainer.php',$Write);
?>

also i copy the code from this video Arduino IDE + NodeMCU V3 + MySQL + PHP | NodeMCU V3 with RFID RC522 uses MySQL Database and PHP - YouTube

2

What is that usage of file_put_contents() function?

Are you overwriting php file with your value. That's a bit pointless and hard to implement, because you need to do still 2 request (one request for reading UID and other request for reading it form other .php file ) or one async request with redirect with using header PHP function for redirect to that .php file that you are overwriting.

Why you just not do simple PHP file where you will have few if statements with output like:

if(value == 1234){
echo "OK";
}else{
echo "NO";
}

And you will be able to read that OK or NO in server response on request. Without any other extra HTML code. You can read response (whole HTML code or just value) using parser with you client by reading server response row by row in while is true client.available() function (when bytes are in buffer), so you will read HTTP header first , then blank row and then response where is your value of HTML code.

3

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