How to retain dropdown selected option after submit / page refresh - php

Question

I want to have dropdown selected option selected after submit/refresh page. I search for other examples but no one works on my code.
How to retain selected value after submit/refresh with this code?
<form name="test" action="test.php?id=<?php echo $row["id"]; ?>" method="post">
<select id="test_email" name="test_email">
<option value="">...select</option>
<?php
$sql2 = "SELECT test_id, test_email FROM test WHERE status='Act'";
$res = $db->query($sql2);
if ($res->num_rows > 0) {
while($row1 = mysqli_fetch_array($res)) {
?>
<option value="<?php echo $row1['test_email'];?>-<?php echo $row1['test_id'];?>"><?php echo $row1['test_id'];?></option>
<?php
}
}
?>
</select>
Solved this way:
Because I could not pass $_POST['test_email'] with <?php echo $row1['test_email'];?>-<?php echo $row1['test_id'];?>
Because I use explode on $_POST['test_email']
I make one more post (insert in db) $test_temp = trim(mysqli_real_escape_string($db, $_POST['test_email'])); to have my dropdown value (whole string) in db.
I added hidden input in my form <input id="test_temp" type="hidden" name="test_temp" value="<?php echo $row["test_temp"]; ?>">
And changed select option line to <option value="<?php echo $row1['test_email'] . '-' . $row1['test_id']; ?>"<?php if($row1['test_email'] . '-' . $row1['test_id'] == $row['test_temp']) echo ' selected="selected"' ; ?>><?php echo $row1['test_id'];?></option>.
Perhaps this could be simpler but it works like a charm.
#roberto06: Thank you for your guidance.

Answer 1

You need to add the selected="selected" attribute on the option matching your $_POST value.
You might also want to concatenate <?php echo $row1['test_email'];?>-<?php echo $row1['test_id'];?> into <?php echo $row1['test_email'] . '-' . $row1['test_id']; ?>, but that's up to you.
Here's a solution (I assumed that $POST['test_email'] has to be equal to $row1['test_email'] . '-' . $row1['test_id'] in order for the condition to be matched). I'm using a shorthand if...else here, but you could also use a classic if :
<form name="test" action="test.php?id=<?php echo $row["id"]; ?>" method="post">
<select id="test_email" name="test_email">
<option value="">...select</option>
<?php
$sql2 = "SELECT test_id, test_email FROM test WHERE status='Act'";
$res = $db->query($sql2);
if ($res->num_rows > 0) {
while($row1 = mysqli_fetch_array($res)) {
?>
<option value="<?php echo $row1['test_email'] . '-' . $row1['test_id']; ?>"<?php echo (isset($_POST['test_email']) && $row1['test_email'] . '-' . $row1['test_id'] == $_POST['test_email']) ? ' selected="selected"' : ''; ?>><?php echo $row1['test_id'];?></option>
<?php
}
}
?>
</select>
</form>