SQL select as a PHP function [duplicate] - php

Question

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Warning: mysqli_query() expects parameter 1 to be mysqli, null given in
(3 answers)
Closed 7 years ago.
I'm selecting data from MySQL. My code looks like this:
$sql = "SELECT oznacenie_odpadu FROM zdroj_dat ORDER by ID ASC";
if ($result = $conn->query($sql)) {
// fetch associative array
while($row = $result->fetch_assoc()) {
echo '<option value="'.$row['oznacenie_odpadu'].'" >'.$row['oznacenie_odpadu'].'</option>';
}
}
This part of code is in my code multiple times. I'm calling it 5times only string "oznacenie_odpadu" is changing. Therefore I made function:
function select($data) {
$sql = "SELECT rozmer FROM zdroj_dat ORDER by id ASC";
if ($result = $conn->query($sql)) {
// fetch associative array
while($row = $result->fetch_assoc()) {
echo '<option value="'.$row[$data].'" >'.$row[$data].'</option>';
}
}
}
Calling it with select("somevalue");
Syntax is ok because I didn't change anything but when I load the page the data from database are not retrieved.

Answer 1

You have a variable scope issue. $conn is not available inside of your function. You need to pass it as a parameter so ic an be used inside of your function.
function select($conn, $data) {
$sql = "SELECT rozmer FROM zdroj_dat ORDER by id ASC";
if ($result = $conn->query($sql)) {
// fetch associative array
while($row = $result->fetch_assoc()) {
echo '<option value="'.$row[$data].'" >'.$row[$data].'</option>';
}
}
}
Call it:
select($conn, "somevalue");