Why does pg_fetch_array returns null despite null check?

Question

I have this php case executed when called by a function in my main page. When I type my variables like this: $tutorReasonString = "I'm fine and working." and $clientReasonString = "I'm fine too, thanks for asking", nothing is wrong here. But when I try to fetch them with pg_fetch_array(), I get NULL values returned.

Note that tutorabsence and clientabsence tables are not connected with any kind of SQL trigger, I only assign them exact same id in another execution which is retrieved from a row of another table with php.

case "absencePc":
                
                $id = array_search(post("id"), $_SESSION["keyhash"]);
                
                $tutorAbsSql = "SELECT reason FROM tutorabsence WHERE id='$id'";
                $tutorReason = pg_query($tutorAbsSql);
                if(pg_fetch_row($tutorReason) == NULL) {
                    
                    $tutorStatus = "0";
                    $tutorReasonString = "";
                    
                } else {
                    
                    $tutorStatus = "1";
                //  $tutorReasonString = "I'm working"; This works  
                
                // This returns null.
                    $tutorReasonFetch = pg_fetch_array($tutorReason);
                    $tutorReasonString = $tutorReasonFetch["reason"];
                    
                   
                };
                
                
                $clientAbsSql = "SELECT reason FROM clientabsence WHERE id='$id'";
                $clientReason = pg_query($clientAbsSql);
                if(pg_fetch_row($clientReason) == NULL) {
                    
                    $clientStatus = "0";
                    $clientReasonString = "";

         
                } else {
                    
                                        
                    $clientStatus = "1";  
                //  $clientReasonString = "I'm working";  This works
                
                // This returns null.
                    $clientReasonFetch = pg_fetch_array($clientReason);
                    $clientReasonString = $clientReasonFetch["reason"];
                   
                    
                };
                
         $response[] = array("tutorReason" => $tutorReasonString,
                             "clientReason" => $clientReasonString,
                             "tutorStatus" => $tutorStatus,
                              "clientStatus" => $clientStatus);
                
                echo json_encode($response);
                
break;

Ever bothered to check the docs on "when" it can return "null"? I mean, it seems silly, but it would be my first step to take too understand a functions behaviour. — Xorifelse
– Xorifelse, Commented Feb 18, 2017 at 22:36
Obviously, I checked that exact page several times before I bothered to ask a question here. There would be things I've missed though. — Ahmet
– Ahmet, Commented Feb 18, 2017 at 22:39
Do you expect multiple reason per $id, or is it just one? — Xorifelse
– Xorifelse, Commented Feb 18, 2017 at 22:44

Xorifelse · Accepted Answer · 2017-02-19 04:50:55Z

2

The problem you're having is that you're fetching twice from 1 result:

$tutorAbsSql = "SELECT reason FROM tutorabsence WHERE id='$id'";
$tutorReason = pg_query($tutorAbsSql);

if(($row = pg_fetch_row($tutorReason)) != false){
  $tutorStatus = "1";
  $tutorReasonString = $row[0];
  print_r($row);
} else {
  $tutorStatus = "0";
  $tutorReasonString = ""; 
}

It internally moves the result pointer forward, then pg_fetch_array() is then fetching for the next value, which does not exist.

edited Feb 19, 2017 at 4:50

answered Feb 18, 2017 at 22:56

Xorifelse

7,9411 gold badge29 silver badges38 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Ahmet Over a year ago

I changed the code the way you suggested it. Strangely, I get undefined index error now, but results are shown in print_r($row). Here is the screenshot.

Xorifelse Over a year ago

I already updated the code, in PostgreSQL it fetches by num, not an assoc array. So its $tutorReasonString = $row[0];

gojiraki Over a year ago

'It internally moves the result pointer forward'. Is there a way to stop this?

Collectives™ on Stack Overflow

Why does pg_fetch_array returns null despite null check?

1 Answer 1

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related