Why the php 'if statement' does not give expected result? - php

Question

I am designing a php application using AJAX and PHP.
But the if statement in my php file behaves unexpectedly.
The request method is 'POST';
Ajax code is
function fetchData(){
var recipename = document.getElementById("recipe").value;
var calorie = false;
createRequestObject();
//window.alert(calorie);
var url = "reciepinfo.php";
xmlHttp.open("POST",url,true);
xmlHttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
window.alert(calorie);
xmlHttp.send("recipe="+recipename+"&calorie="+calorie);
xmlHttp.onreadystatechange = function(){
if(xmlHttp.readyState===4 && xmlHttp.status===200){
document.getElementById("target").innerHTML = xmlHttp.responseText;
}
}
}
And php code is:
<?php
$_SESSION['flag']=false;
if($_SESSION['flag']==false){
session_start();
$_SESSION['flag']=true;
}
$recipename = $_REQUEST['recipe'];
$calorie = $_REQUEST['calorie'];
echo $calorie;
$calorietemp = 0;
//echo $recipename;
$database = "nutrition";
$link = mysqli_connect('localhost','root','',$database);
$query = "select * from recipestb where name='$recipename'";
//$result = mysqli_query($link,$query);
//$obj = mysqli_fetch_object($result);;
if($link){
$result = mysqli_query($link,$query);
$obj = mysqli_fetch_object($result);
//$arr = mysqli_fetch_array($result);
//$names = "";
if(is_object($obj)){
echo "<i/>";
echo "<font size='5'>";
echo "Recipe name: ".$obj->name;
echo '<br/>';
echo "Carbohydrates : ".$obj->carbs." grams";
echo '<br/>';
echo "Proteins: ".$obj->protein." grams";
echo '<br/>';
echo "Fat: ".$obj->fat." grams";
echo '<br/>';
echo "Calories: ".$obj->calorie." cal";
$calorietemp = $obj->calorie;
echo '<br/>';
}else{
echo "non object";
}
}else{
echo "Connection failed";
}
if($calorie==true){
echo $calorie;
$_SESSION['caloriecount'] = $_SESSION['caloriecount'] + $calorietemp;
echo "Total calorie in diet :".$_SESSION['caloriecount'];
}
My session handling is weird i accept, but neglecting that, even the variable calorie is explicitly set to false, the if block executes.The echo $calorie statement also executes and it displays $calorie as false.
And i am not getting what is going wrong exactly.
Almost irritated with this.
Can anybody help?
EDIT1:
The php code is fine...
Ajax code has some problem...
When i set the $calorie to false in php code..
It behaved properly..

Answer 1

Leaving the session handling aside, the $calorie problem ...
You pass the data via AJAX as strings.
$calorie = 'false';
var_dump((true == $calorie));
You will get always bool(true). Using your AJAX example above, try this snippet instead (and use POST instead of REQUEST):
$calorie = ('true' == $_POST['calorie']);
var_dump($calorie);
// produces `bool(false)`

Answer 2

As a beginner i was unaware that the java-script variable with value false is passed as a string "false" to a server side script like PHP.
If we use a boolval(), in PHP this issue can be resolved.
PHP boolval()
I set the $calorie in my java-script to 0 or 1 as per my need.
When i wanted the false value to be sent to PHP script ,i set $calorie in java-script to 0 and the boolval() in corresponding PHP script evaluated it as false.
So the issue was resolved.