PHP beginner with MySQL trouble - php

Question

I am creating a website in which users can log on and review Tablet PC's
On tablet page visitors to the site can see the reviews left by other users. Despite users being able to review 5 tablets, the 'ipad' page for example will only show 'ipad' review. The code can be seen below:
<?php
include('connection.php');
$result = mysql_query("SELECT * FROM tt_review WHERE product = 'Apple iPad'");
echo "<table border='1'>
<tr>
</tr>";
while($row = mysql_fetch_array($result)) //This function is calling the results variable and displaying them within the rows below
{
echo "<tr>"; //this code tells the page to output the table rows that are defined above
echo "<td>" . $row['name'] . "</td>";
echo "<td>" . $row['date'] . "</td>"; //each row is then executed using the table data function
echo "<td>" . $row['product'] . "</td>";
echo "<td>" . $row['star'] . "</td>";
echo "<td>" . $row['comment'] . "</td>";
echo "</tr>";
}
echo "</table>";
?>
I have a field in my database called 'star' which is the rating the users have gave the tablet. 1, 2, 3, 4 or 5 are the options. I need code that works out the average of the 'star' rating from the 'ipad' page and to display an image based on whatever number it is.
All help is greatly appreciated as I am a newcomer and cant seem to find the answer online.
Thanks
Jonathan

Answer 1

Use mysqli to connect to the database. Then you can use the AVG function to calculate average of the column star. Execute the query and fetch the array and then print the average. Then you can use simple switch case or if else to display the image according to the average obtained.
<?php
$db = mysqli_connect("host","user","pass","database");
$query = "SELECT AVG(column_name) FROM table_name";
$result = mysqli_query($db, $query);
$array = mysqli_fetch_row($result);
$average = $array[0];
echo $average;
?>

Answer 2

From what I understand you want to calculate the average rating for each tablet. If yes, you can just fetch the star column for the particular tablet from the database and extract it as an array and run a simple for-each loop to calculate the sum and average of the rating for that tablet and based on the average it calculated, an indication can be placed on the screen in the form of images or something else.

Answer 3

I'm with the others regarding using 'mysql_*' functions, but I won't go into that here as that is not relevant to your question.
To find the average you add all of the total stars together and divide by the quantity. My suggestion is to first find out how many rows are returned.
$totalStars = count($result);
You also need to know what the sum is of the column. This is done using SUM(column). Like so:
$result = mysql_query("SELECT SUM(star) as TotalStars, name, date, product, star, comment FROM tt_review WHERE product = 'Apple iPad'");
However, you can also add a counter to your code, like so:
$x = 0;
while($row = mysql_fetch_array($result)) {
$x += $row['star'];
// your other code
$x++;
}
Finally, at the end, you can display the average by doing something like:
if ($totalStars != 0 ) {
$average = $x / $totalStars;
echo "This product's average stars is " . $average . PHP_EOL;
} else {
// handle the divide by zero issue
}
When it comes to displaying a particular image, well, you can use a conditional statement or something like:
if ($average > 0 && $average <= 1) {
echo "<img src='images/star1.jpg' alt='star1' />";
} else if ($average > 1 && $average <= 1.5) {
// etc etc etc
}
Hope that helped some.

Answer 4

As mentioned, use PDO to connect to the database. Here's how you get the average stars:
$i = 0;
$totalStars = 0;
while($row = mysql_fetch_array($result))
{
$totalStars += $row['star'];
// rest of your code
$i++;
}
echo 'Average stars = '.($totalStars/$i);

Answer 5

As pointed out by others, Mysql has an AVG() function you can use for this exact purpose.
SELECT AVG(star) AS rating FROM tt_review WHERE product = 'Apple iPad' GROUP BY product;
or, to get the star rating for all products you leave off the WHERE
SELECT AVG(star) AS rating FROM tt_review GROUP BY product;
If you just want your rating to be 1,2,3,4, or 5
SELECT ROUND(AVG(star), 0) AS rating FROM tt_review WHERE product = 'Apple iPad' GROUP BY product;
And if you want the rounded number to skew up (a common desire)
SELECT CEILING(AVG(star)) AS rating FROM tt_review WHERE product = 'Apple iPad' GROUP BY product;