Connection to a DB

[snowymasta]

Hi Guys,

need a little help and drawn a blank. The code that is not working is below

$result = $conn->query("SELECT * FROM MK_migration_details WHERE mig_bid='".$_SESSION['bid']."'");

I can confirm the $_SESSION['bid'] is working as echo's out on another part of the page. and the above $result works when i manually type the search criteria like below.

$result = $conn->query("SELECT * FROM MK_migration_details WHERE mig_bid='300101'");

Basically no result turn up on the page. Any ideas or advise how I can diagnose?

[Barand]

Check for mysql error messages
 

print_r($conn->errorInfo())   // PDO

echo $conn->error;            // mysqli

 

[snowymasta]

tried it and nothing throws out

[Barand]

What if you echo the query string to examine the syntax?

echo "SELECT * FROM MK_migration_details WHERE mig_bid='".$_SESSION['bid']."'";

 

Edited November 20, 2020 by Barand

[snowymasta]

Ok that worked and it does exactly what it should, so assume that means the error is elsewhere! Whole Script below

 

<?php
require_once("db_connection.php");

$conn = new mysqli($servername, $username, $password, $dbname) or die("Connect failed: %s\n". $conn -> error);

$result = $conn->query("SELECT * FROM MK_migration_details WHERE mig_bid='".$_SESSION['bid']."'");

    $data = array();
    while($row = $result->fetch_assoc()) {
        $data[] = $row;
    }
    echo json_encode($data);
?>

[Barand]

I don't see any error check after the query() call.

Easier than checking all mysqli calls is to put this line of code before the "new mysqli()" line ...

mysqli_report(MYSQLI_REPORT_ERROR|MYSQLI_REPORT_STRICT);

 

[snowymasta]

you mean like the below?

 

mysqli_report(MYSQLI_REPORT_ERROR|MYSQLI_REPORT_STRICT);

$conn = new mysqli($servername, $username, $password, $dbname) or die("Connect failed: %s\n". $conn -> error);

$result = $conn->query("SELECT * FROM MK_migration_details WHERE mig_bid = '".$_SESSION['bid']."'");
 

[Barand]

yes, and make sure your php error reporting is on.

[mac_gyver]

the value probably contains some non-printing character(s). what does var_dump($_SESSION['bid']); show?

[snowymasta]

Hi Mac_gyver

it shows this 

string(6) "300101"

 

The DB structure is

mig_bidvarchar(255)utf8_general_ciNoNone 

Edited November 20, 2020 by snowymasta

[mac_gyver]

that's an acceptable var_dump() output. the length matches the number of displayed characters.

i suspect you are seeing the result of two (or more) requests to the page. for the first request, there is an input value and when you are using echo/var_dump to display it, this is preventing a header() redirect, that's causing additional request(s), which don't have the expected input. you are seeing the displayed result from the last request made. this 'works' when you hard-code the value, since all requests have the input value.

so, two things -

1. if it sounds like your code is capable of doing this, you will need to find and fix what's causing the additional request(s) and if you cannot determine what's causing the problem, you will need to post all of the code needed to reproduce the problem.
2. you should always validate all inputs before using them (yes a session variable is an input to your code) and setup/display a message letting the visitor know that a 'required' input is not present.

lastly, why is this value in a session variable at all. that's generally a sign that you are doing something in the hardest way possible.

Edited November 21, 2020 by mac_gyver

[snowymasta]

On 11/21/2020 at 1:13 AM, mac_gyver said:

that's an acceptable var_dump() output. the length matches the number of displayed characters.

i suspect you are seeing the result of two (or more) requests to the page. for the first request, there is an input value and when you are using echo/var_dump to display it, this is preventing a header() redirect, that's causing additional request(s), which don't have the expected input. you are seeing the displayed result from the last request made. this 'works' when you hard-code the value, since all requests have the input value.

so, two things -

1. if it sounds like your code is capable of doing this, you will need to find and fix what's causing the additional request(s) and if you cannot determine what's causing the problem, you will need to post all of the code needed to reproduce the problem.
2. you should always validate all inputs before using them (yes a session variable is an input to your code) and setup/display a message letting the visitor know that a 'required' input is not present.

lastly, why is this value in a session variable at all. that's generally a sign that you are doing something in the hardest way possible.

Thank you for your advise on this really appreciated, The session is being created at a login script I have and then passes that business ID through the pages.