在for循环javascript中显示唯一值

Question

I'm trying to display unique value in for loop per below. The data is retrieved from mysql. Currently, it's displaying all the values in this column (Book Name) but just want to show just unique value and remove any duplicated values from displaying.

<?php
$i=0;
while($rows=mysql_fetch_array($result))
{
$roll1[$i]=$rows['bkname'];
$i++;
}
$total_elmt=count($roll1);
?>
<form method="POST" action=" ">
<select name="sel1" id="sel1">
<option value="Select Book Name">Book Name</option>
<?php 
for($j=0;$j<$total_elmt;$j++)
{
?><option><?php 
echo $roll1[$j];
?></option><?php
}
?>
</select>
</form>

Answer 1

Instead of removing duplicates in the PHP, you could just use a DISTINCT clause in your query:

<?php

$db = new mysqli('localhost', 'username', 'password', 'database_name');
// $sql = 'SELECT DISTINCT(bkname) FROM your_table_name';
$sql = 'SELECT * FROM your_table_name GROUP BY bkname';
$query = mysqli_query($db, $sql);

?>

<form method="POST" action="">
    <select name="sel1" id="sel1">
        <option disabled selected>Book Name</option>
        <?php while($row = mysqli_fetch_assoc($query)): ?>
            <option value="<?php echo $row['bkname']; ?>"><?php echo $row['bkname']; ?></option>
        <?php endwhile; ?>
    </select>
</form>

Obligatory Note:

Please, don't use mysql_* functions in new code. They are no longer maintained and are officially deprecated. See the red box? Learn about prepared statements instead, and use PDO or MySQLi - this article will help you decide which. If you choose PDO, here is a good tutorial.

_{Ref: https://stackoverflow.com/a/12860140/3859027}