how to fix undefined index $user = $_GET['user'];

Question

<?php
header('Access-Control-Allow-Origin: *');
header('Access-Control-Allow-Methods: GET, POST, PATCH, PUT, DELETE, OPTIONS');
header('Access-Control-Allow-Headers: Origin, Content-Type, X-Auth-Token');
header("Content-Type: application/json; charset=UTF-8");

include("global.php");

$conn = new mysqli(server, dbuser, dbpw, db);

$user = $_GET['user'];
//$customer = $_GET['customer'];
$querystring = "";
$querystring = "SELECT email, password, firstname, lastname from user ";
$result = $conn->query($querystring);



$outp = "[";
while($rs = $result->fetch_array(MYSQLI_ASSOC)) {
    if ($outp != "[") {$outp .= ",";}
    $outp .= '{"email":"'  . $rs["email"] . '",';
    $outp .= '"password":"'  . $rs["password"] . '",';
    $outp .= '"firstname":"'   . $rs["firstname"] . '",';   
    $outp .= '"lastname":"'   . $rs["lastname"]. '"}';
}
$outp .="]";

$conn->close();

echo($outp);
?>

This is the PHP code in the database and need to use get method. the error shows undefined index : $user = $_GET['user']; when I run it shows this error. How to fix it?

Clear this line-> $user = $_GET['user']; ..You don't us of $user variable. — pedram shabani, Nov 20 '18 at 06:11

score 0 · Answer 1 · answered Nov 20 '18 at 06:15

I added the IF condition in below code you can check it. By adding this condition you are able to solve the undefine index issue

<?php
header('Access-Control-Allow-Origin: *');
header('Access-Control-Allow-Methods: GET, POST, PATCH, PUT, DELETE, OPTIONS');
header('Access-Control-Allow-Headers: Origin, Content-Type, X-Auth-Token');
header("Content-Type: application/json; charset=UTF-8");

include("global.php");

$conn = new mysqli(server, dbuser, dbpw, db);
if(!isset($_GET['user']) && empty($_GET['user']))
return false;// this will send back if data or index is not found and also solve the undefine index problem
$user = $_GET['user'];
//$customer = $_GET['customer'];
$querystring = "";
$querystring = "SELECT email, password, firstname, lastname from user ";
$result = $conn->query($querystring);



$outp = "[";
while($rs = $result->fetch_array(MYSQLI_ASSOC)) {
    if ($outp != "[") {$outp .= ",";}
    $outp .= '{"email":"'  . $rs["email"] . '",';
    $outp .= '"password":"'  . $rs["password"] . '",';
    $outp .= '"firstname":"'   . $rs["firstname"] . '",';   
    $outp .= '"lastname":"'   . $rs["lastname"]. '"}';
}
$outp .="]";

$conn->close();

echo($outp);
?>

after i add the if statement. it return empty. nothing show. — yangmy, Nov 20 '18 at 11:15
means you are not getting any value in GET. Can you print $_GET and paste the print string here so i can check — pawansgi92, Nov 20 '18 at 17:22

score 0 · Accepted Answer · answered Nov 20 '18 at 07:15

You can fix this issue by add isset in $_GET['user'] and check its empty or not

<?php
header('Access-Control-Allow-Origin: *');
header('Access-Control-Allow-Methods: GET, POST, PATCH, PUT, DELETE, OPTIONS');
header('Access-Control-Allow-Headers: Origin, Content-Type, X-Auth-Token');
header("Content-Type: application/json; charset=UTF-8");

include("global.php");

$conn = new mysqli(server, dbuser, dbpw, db);

if( isset($_GET['user']) && $_GET['user']!='' ){
    $user = $_GET['user'];
}else{
    $user='';
}
//$customer = $_GET['customer'];
$querystring = "";
$querystring = "SELECT email, password, firstname, lastname from user ";
$result = $conn->query($querystring);

    enter code here

$outp = "[";
while($rs = $result->fetch_array(MYSQLI_ASSOC)) {
    if ($outp != "[") {$outp .= ",";}
    $outp .= '{"email":"'  . $rs["email"] . '",';
    $outp .= '"password":"'  . $rs["password"] . '",';
    $outp .= '"firstname":"'   . $rs["firstname"] . '",';   
    $outp .= '"lastname":"'   . $rs["lastname"]. '"}';
}
$outp .="]";

$conn->close();

echo($outp);
?>

Another way is that you can add @ in front of $_GET['user']

<?php
header('Access-Control-Allow-Origin: *');
header('Access-Control-Allow-Methods: GET, POST, PATCH, PUT, DELETE, OPTIONS');
header('Access-Control-Allow-Headers: Origin, Content-Type, X-Auth-Token');
header("Content-Type: application/json; charset=UTF-8");

include("global.php");

$conn = new mysqli(server, dbuser, dbpw, db);

@$user = $_GET['user'];

//$customer = $_GET['customer'];
$querystring = "";
$querystring = "SELECT email, password, firstname, lastname from user ";
$result = $conn->query($querystring);

    enter code here

$outp = "[";
while($rs = $result->fetch_array(MYSQLI_ASSOC)) {
    if ($outp != "[") {$outp .= ",";}
    $outp .= '{"email":"'  . $rs["email"] . '",';
    $outp .= '"password":"'  . $rs["password"] . '",';
    $outp .= '"firstname":"'   . $rs["firstname"] . '",';   
    $outp .= '"lastname":"'   . $rs["lastname"]. '"}';
}
$outp .="]";

$conn->close();

echo($outp);
?>

score -1 · Answer 3 · edited Nov 22 '18 at 21:15

There are many ways to check if an array's index is undefined. The example below uses two methods: isset and empty.

The call to isset returns true if the array has the specified key.

The call to empty will return true if the value for the specified index is "empty" (null, empty string, zero, empty array, etc...) or if the specified key does not exist.

    <?php
    header('Access-Control-Allow-Origin: *');
    header('Access-Control-Allow-Methods: GET, POST, PATCH, PUT, DELETE, OPTIONS');
    header('Access-Control-Allow-Headers: Origin, Content-Type, X-Auth-Token');
    header("Content-Type: application/json; charset=UTF-8");

    include("global.php");

    $conn = new mysqli(server, dbuser, dbpw, db);

    $user = isset($_GET['user'])&&!empty($_GET['user']) ? $_GET['user'] : NULL;
    //$customer = $_GET['customer'];
    $querystring = "";
    $querystring = "SELECT email, password, firstname, lastname from user ";
    $result = $conn->query($querystring);



    $outp = "[";
    while($rs = $result->fetch_array(MYSQLI_ASSOC)) {
        if ($outp != "[") {$outp .= ",";}
        $outp .= '{"email":"'  . $rs["email"] . '",';
        $outp .= '"password":"'  . $rs["password"] . '",';
        $outp .= '"firstname":"'   . $rs["firstname"] . '",';   
        $outp .= '"lastname":"'   . $rs["lastname"]. '"}';
    }
    $outp .="]";

    $conn->close();

    echo($outp);
    ?>

Can you add some explanation to your code such that others can learn from it? — Nico Haase, Nov 22 '18 at 07:20

how to fix undefined index $user = $_GET['user'];

3 Answers3