SQL选择作为PHP函数[重复]

Question

This question already has an answer here:

• Warning: mysqli_query() expects parameter 1 to be mysqli, null given in 3 answers

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.

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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");