Extracting values from a database to populate a dropdown - php

Question

I have a db, am trying to extract values into a list
Here is the code I am trying to run (I had to adapt it from elsewhere), which should return an array, from which I want to select the AllianceName attribute
<?php
//database connection file setting.inc will need to be modified for production
include ("settings.inc");
$con = mysqli_connect("$dbhost", "$dbuser", "$dbpass");
if (!$con) {
exit('Connect Error (' . mysqli_connect_errno() . ') '
. mysqli_connect_error());
}
//set the default client character set
mysqli_set_charset($con, 'utf-8');
mysqli_select_db($dbname, $con);
$options = array();
$options[] = "<option value=''>--?--</option>";
$query = "
SELECT *
FROM `City`
GROUP BY `AllianceName`
";
$db = mysqli_query($query);
foreach ( $db as $d ) {
$options[] = "<option value='{".$d['AllianceName']."}'></option>";
}
?>
<select class="" id="articles" size="1" name="articles">
<?php echo implode("\n", $options); ?>
</select>*/
Right now this only returns the --?-- that I have defined in the options array. It does not parse any of the values from the query. I know the query by itself is correct since I have run it exactly in this syntax in the SQL server and it works.
I am pretty sure that this is a syntax error ... var_dump($db) gives me a bool(false) output.
Here's the latest code I am using:
<?php
//database connection file setting.inc will need to be modified for production
include ("settings.inc");
$db = new mysqli($dbhost, $dbuser, $dbpass, $dbname);
if($db->connect_errno > 0){
die('Unable to connect to database [' . $db->connect_error . ']');
}
?>
<select class="Select" id="articles" size="1" name="articles">
<?php
$sql = <<<SQL
SELECT DISTINCT `AllianceName`
FROM `City`
SQL;
if(!$result = $db->query($sql)){
die('There was an error running the query [' . $db->error . ']');
}
while($row = $result->fetch_assoc()){
echo "<option value="'.{$row['AllianceName']}.'"></option>";
}
?>
</select>
The query by itself runs fine when I just echo the results. Trying to put it into a dropdown fails every time. No values get populated.

Answer 1

There are a couple problems here.
First you don't need the GROUP BY 'AllianceName' in your query, you are not performing any functions on your data, that might have been causing you to not return any results.
Secondly, normally you loop through query results with a while loop. You don't have to, but its common practice, so your code should look like this..
<?php
//database connection file setting.inc will need to be modified for production
include ("settings.inc");
$con = mysqli_connect("$dbhost", "$dbuser", "$dbpass", "$dbname");
if (!$con) {
exit('Connect Error (' . mysqli_connect_errno() . ') '
. mysqli_connect_error());
}
//there is no need to make an array first, just have it spit out the options if you aren't making a class or function
?>
<select class="" id="articles" size="1" name="articles">
<?php
$query = "SELECT * FROM `City` ";
$db = mysqli_query($query);
while ( $d=mysqli_fetch_assoc($db)) {
echo "<option value='{".$d['AllianceName']."}'></option>";
}
?>
</select>
Try that out and see if it works for you.

Answer 2

From the mysqli_query() docs:
Returns FALSE on failure. For successful SELECT, SHOW, DESCRIBE or
EXPLAIN queries mysqli_query() will return a mysqli_result object. For
other successful queries mysqli_query() will return TRUE.
So what you have after the query succeeded is a mysqli_result object. Now you have to fetch the result into an (associative) array or object, row by row.
if($query === false) die('Query failed to execute');
while($row = $result->fetch_assoc()) {
echo $row['AllianceName'] . PHP_EOL;
}
All this is described in hundreds of tutorials in the web, so please read one of these. I recommend these written in the current decade, e.g. http://codular.com/php-mysqli

Answer 3

Here is the code that finally worked. Both #Syndrose and #Zombiehunter provided clues to this.
#Syndrose - you might want to take into account the syntax used here as this is what was failing from your codebase...especially the syntax for the echo tag line.
<?php
//database connection file setting.inc will need to be modified for production
include ("settings.inc");
$db = new mysqli($dbhost, $dbuser, $dbpass, $dbname);
if($db->connect_errno > 0){
die('Unable to connect to database [' . $db->connect_error . ']');
}
$sql = <<<SQL
SELECT DISTINCT `AllianceName`
FROM `City`
SQL;
if(!$result = $db->query($sql)){
die('There was an error running the query [' . $db->error . ']');
}
?>
<select style="width:300px" class="" id="AllianceName" size="1" name="Alliance Name">
<?php
while($row = $result->fetch_assoc()){
echo '<option value='.$row['AllianceName'].'>'.$row['AllianceName'].'</option>';
}
?>
</select>