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

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..

I suspect this might have to do with variable types. Are you sure $calorie is a boolean? If it has the string value "false", it would evaluate to boolean true in the if-statement, but still come out as false when you echo. — Anders
– Anders, Commented Oct 31, 2015 at 12:18
Not sure the type information is preserved through the AJAX call to the PHP. Try running $calorie = (strtolower($calorie) === 'true'? true: false;); somewhere before the if statement. Not sure about this, though. Just guessing. But it is worth a try. — Anders
– Anders, Commented Oct 31, 2015 at 12:23
Glad that you solved the issue! Instead of editing the question, you should post your solution to the problem as an answer, and accept it (or some other answer that helped). — Anders
– Anders, Commented Nov 1, 2015 at 2:01

jpaljasma · Accepted Answer · 2015-10-31 12:29:08Z

2

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)`

edited Oct 31, 2015 at 12:29

answered Oct 31, 2015 at 12:21

jpaljasma

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6 Comments

jpaljasma Over a year ago

I know ... revised my posting - your problem is $_POST variable handling and types. false and 'false' have different meaning.

Deepeshkumar Over a year ago

That might be the issue let me check.. wait

Deepeshkumar Over a year ago

I used $calorie = boolval($_POST['calorie']); And passed '1' and '0' values as $calorie using java-script as per requirement. And problem solved! Sorry for the trouble

jpaljasma Over a year ago

boolval is good idea, yet available PHP > 5.5. hint: Vote up anyone who helped :)

Deepeshkumar Over a year ago

Haven't tried your solution.. Will try n let you know.. Thank you!

|

Deepeshkumar · Accepted Answer · 2015-11-01 02:35:44Z

0

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.

answered Nov 1, 2015 at 2:35

Deepeshkumar

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