SQL result array, from PDO query, has duplicated values [duplicate] - php

Question

This question already has answers here:
sql PDO fetchall duplicate object keys?
(2 answers)
Closed 2 years ago.
I have a mysql table that has the following fields
STUDENTID | FIRSTNAME | SURNAME | DOB | SCHOOLID
A form is used for a user to search for a student and output all those with matching first and surnames
The following SQL statement returns the PDO fine
$sqlstmnt2 = 'SELECT * FROM students WHERE firstName = :fname AND surname = :sname AND schoolID = :schoolID';
// prepare PDOstatement as $query ...
// ...
$query->execute();
$_SESSION['foundPupils'] = $query->fetchAll();
However, when I pass this through to another PHP page in a session variable, I'm confused as to how to access each field individually. I have the following code
foreach($_SESSION['foundPupils'][0] as $found){
echo($found);
}
This outputs the found data but the issue is that it outputs it twice, and it's just a long string of data which can't be formatted nicely. My questions are:
Why does each result output twice?
How do I access the individual fields within this array (kind of like foundPupils[0]['firstName'] for example?

Answer 1

According to the documentation, both the method PDOStatement::fetch and PDOStatement::fetchAll accepts a $fetch_style parameter. If not set, the default value is PDO::FETCH_BOTH. That means the fetched array will both reference the fields by position (e.g. 0, 1, 2) and by column name (e.g. "firstName", "surname").
So by default, your fetched results would be something like this:
Array
(
[0] => Array
(
[name] => apple
[0] => apple
[colour] => red
[1] => red
)
[1] => Array
(
[name] => pear
[0] => pear
[colour] => green
[1] => green
)
[2] => Array
(
[name] => watermelon
[0] => watermelon
[colour] => pink
[1] => pink
)
)
To fix this, you need to call your fetch function (I suppose it is PDOStatement::fetchAll) with PDO::FETCH_COLUMN as the fetch style:
$query->execute();
$_SESSION['foundPupils'] = $query->fetchAll(PDO::FETCH_COLUMN);

Answer 2

Query results are returned and stored in a result object. Therefore, you have to iterate through the result either using xxxx_fetch_array or xxxx_fetch_row. for example
$sql='SELECT * FROM table_name';
$result = mysqli_query($conn,$sql);
while($row=mysqli_fetch_array($result)){
echo $row['COLUMN_NAME'].'<br />';
}