anexo anexo - 2 months ago 16
MySQL Question

Foreach, for loop PHP redundancy

I have the following code:

<select multiple="multiple">
<?php $sql = "SELECT book_id, book_name FROM book ORDER BY book_name";
try {
$conn = new PDO("...");
$conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

foreach ($conn->query($sql) as $row) {
$myId = $row['book_id'];
$myName = $row['book_name'];
for ($i = 0; $i < count($array); $i++) {
if ($myId != $array[$i]) {
echo("<option value='$myId'>$myName</option>");
}
}
}
}
catch(PDOException $e) {
...
}
$conn = null;
?>
</select>


My purpose is to have a selector , where the not previously associated books with the user appear. In this case, the $array holds the Id of the books that are already link to this user.

I know the problem is the nested loop, because I got the result I want, eg (for a $row = 3 and a $i = 2):

Book1
Book1
Book2
Book2
Book3
Book3


And the desired result would be:

Book1
Book2
Book3


But I can't figured out how to compared the Id's, without nesting the loops.

Answer

instead of your for-loop

  for ($i = 0; $i < count($array); $i++) {
                    if ($myId != $array[$i]) {
                        echo("<option value='$myId'>$myName</option>");
                    }
                }

try in_array() instad:

if(!in_array($myId, $array)) {
    echo("<option value='$myId'>$myName</option>");
}

even if $array contains $id multiple times, this will only write once.

edit: forgot the ! to negate. the condition.