function to select user id and output selected data with mysqli

Question

I have a function as below, but when I echo $user_data['first_name']; it pop out

Undefined index: first_name.

can anyone help out?

$user_data = user_data($con, $user_id, $fields);

echo $user_data['first_name'];
// pop out error Undefined index: first_name.



function user_data($con, $user_id, $fields) {

    $data = array();
    $fields = implode(', ', $fields);
    $result = mysqli_query($con, "SELECT $fields FROM users WHERE user_id= $user_id");
    while ($row = mysqli_fetch_assoc($result)) {
        $data[] = $row;
    } 

    return $data;

} 

$con = new mysqli('localhost', 'username', 'password', 'database_name');

$fields = array('first_name', 'last_name','color');

$user_id = 1;

$data = user_data($con, $user_id, $fields);

Please educate yourself on SQL injection. Your code is vulnerable. — Björn Tantau, Aug 05 '17 at 05:50
@BjörnTantau please feel free to comment my sql injection to educate me :) — Ron Pang, Aug 07 '17 at 09:56
Never ever use variables directly in SQL queries. It enables an attacker to control your database with his own queries. Always use prepared statements with value placeholders. — Björn Tantau, Aug 07 '17 at 10:06
@BjörnTantau do u got any example i can look at it? thanks in advance! — Ron Pang, Aug 09 '17 at 03:18
https://stackoverflow.com/questions/60174/how-can-i-prevent-sql-injection-in-php — Björn Tantau, Aug 09 '17 at 17:06

score 0 · Answer 1 · answered Aug 04 '17 at 06:12

0

Because you will get data in array. So you need to traverse from other. Change your code like:

$user_data = user_data($con, $user_id, $fields);
foreach($user_data as $user){
  echo $user['first_name'];  
}

answered Aug 04 '17 at 06:12

B. Desai

16,414
5
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score 0 · Accepted Answer · answered Aug 04 '17 at 06:15

0

Try this:

echo $user_data[0]['first_name'];

answered Aug 04 '17 at 06:15

TheCleverIdiot

412
4
19

score 0 · Answer 3 · answered Aug 04 '17 at 06:16

The connection is created at the last line in the script given and after that only the database can be accessed so echo the result after using array traversal loops like Foreach,etc. Add this line at the end of your script:

foreach($user_data as $user){
  echo $user['first_name'];  
}

function to select user id and output selected data with mysqli

3 Answers3