[SOLVED] Logic Problem

[will35010]

I'm trying to write a script to calculate miles-per-gallon. Seems easy enough...lol. I have this code so far and I'm having trouble calling the results from the query. I want it to run the query and put the results into an array for calculating the mpg of a specific vehicle. Any direction would be helpful. Thanks.

 

<?php
//script to calculate fuel mileage

//retrieve value from web form
$vin = $_GET['vin'];

// formula to calculate mpg
// mpg = miles / gallons

//db connection info
require('../config.php');
require('../opendb.php');

//Query to pull fuel data

$sql = "SELECT mileage, gallons FROM fuel WHERE vin = '$vin' ORDER BY `date` DESC LIMIT 2";

//send query to database
mysqli_query($conn, $sql) or die('Error: ' . mysql_error());

$data = mysqli_fetch_array($sql);

echo $data[mileage];

?>

 

When the query is ran it displays this:

 

mileage gallons

100050 14.26

100003 14.26

 

[RussellReal]

first question, is mileage only increasing?

 

or could some be like

 

95

100

92

85

 

and does gallons represent the gallons left in the tank, or the gallons used?

 

[will35010]

first question, is mileage only increasing?

 

or could some be like

 

95

100

92

85

 

and does gallons represent the gallons left in the tank, or the gallons used?

 

It should only increase. The gallons represent the fuel added to the tank at time of fueling. I think my problem is in sorting the data from the query. If I could figure out how to sort it, I could then assign variables and do the math.

[RussellReal]

ok so from 100003 to 100050 you used 14.26 gallons of gas, is what thats saying?

[will35010]

ok so from 100003 to 100050 you used 14.26 gallons of gas, is what thats saying?

 

Correct.

[RussellReal]

<?php
$miles = ($gallons = array());
while ($r = mysql_fetch_assoc()) {
	$miles[] = $r['mileagle'];
	$gallons[] = $r['gallons'];
}
$mileGauge = array_pop($miles) - $miles[0];
array_shift($gallons);
$tg = 0;
foreach ($gallons as $v) {
	$tg += $v;
}
$mpg = $mileGauge / $tg;
?>

[will35010]

So my code should be this? It gave me a blank result.

<?php
//script to calculate fuel mileage

//retrieve value from web form
$vin = $_GET['vin'];

//db connection info
require('../config.php');
require('../opendb.php');

//Query to pull fuel data

$sql = "SELECT mileage, gallons FROM fuel WHERE vin = '$vin' ORDER BY `date` DESC LIMIT 2";

//send query to database
mysqli_query($conn, $sql) or die('Error: ' . mysql_error());


$miles = ($gallons = array());
while ($r = mysql_fetch_assoc()) {
   $miles[] = $r['mileage'];
   $gallons[] = $r['gallons'];
}
$mileGauge = array_pop($miles) - $miles[0];
array_shift($gallons);
$tg = 0;
foreach ($gallons as $v) {
$tg += $v;
}
$mpg = $mileGauge / $tg;

echo $mpg;

?>

 

[RussellReal]

I'm not sure you're pulling the data correctly, I did a quick check and 'mysqli_query' doesn't exist

[RussellReal]

sorry for double post.. if you want to add me to MSN add me, I hafta sleep. sorry

RussellonMSN@hotmail.com

[will35010]

I'm not sure you're pulling the data correctly, I did a quick check and 'mysqli_query' doesn't exist

 

It does.

 

http://us2.php.net/manual/en/mysqli.query.php

[will35010]

sorry for double post.. if you want to add me to MSN add me, I hafta sleep. sorry

RussellonMSN@hotmail.com

 

I got it working like this. Thanks for all your help!!!

 

<?php
//script to calculate fuel mileage

//retrieve value from web form
$vin = $_GET['vin'];

//db connection info
require('../config.php');
require('../opendb.php');

//Query to pull fuel data

$sql = "SELECT mileage, gallons FROM fuel WHERE vin = '$vin' ORDER BY `date` DESC LIMIT 2";

//send query to database
$result = mysqli_query($conn, $sql) or die('Error: ' . mysql_error());


$miles = ($gallons = array());
while ($r = mysqli_fetch_assoc($result)) {
   $miles[] = $r['mileage'];
   $gallons[] = $r['gallons'];
}
$mileGauge = array_pop($miles) - $miles[0];
array_shift($gallons);
$tg = 0;
foreach ($gallons as $v) {
$tg += $v;
}
$mpg = $mileGauge / $tg;

echo $mpg;

?>