Question

I am brand new to PHP and mysql and am trying something here. In my HTML, I have one form where I enter a mileage and it’s passed on to the PHP code and converted to an integer. Then I want to take that and check against the database to isolate the record I want so I can do some computations. In other words, if the mileage entered (I save it in a veriable called $term) is less than or equal to a mileage in the table, I want to use the record that matches this criteria. For example, I enter 45 miles and the table has records at 40 miles and 50 miles, I want to pick the 50 mile level. If the user puts in 51, I want to use the 50 level. Things like that.

It connects to the database nicely but I’m not sure how to structure this at the foreach statement.
I have the following:

$term = (int)$_POST['term'];

try {
    $dbh = new PDO("mysql:host=$hostname;dbname=ratetable", $username, $password);

    /*** The SQL SELECT statement ***/
    $sql = "SELECT * FROM rates WHERE mileage<=term";
    foreach ($dbh->query($sql) as $row)
        {
        print $row['mileage'] .' - '. $row['ratepermile'] . '<br />';
        }

    /*** close the database connection ***/
    $dbh = null;
}

When I do this, I get an invalid argument supplied foreach().

Then I started looking around and saw statements that look like this:

$stmt = $db->prepare( 'SELECT * FROM rates WHERE mileage<=:term' );

where the search parameter is passed and so on.

So now I’m confused about what the correct way is to select a single record in an ascending list of mileages in a database (the last matching record versus all that match) that satisfies a criteria or how to correctly structure the WHERE argument. Any suggestions?

Thank you for looking.

Answer 1

What you would need to do is use a WHERE clause in combination with ORDER BY and LIMIT clauses. For example to get the highest value that is less than or equal to a given search criteria you would do:

SELECT * FROM rates
WHERE mileage <= ?
ORDER BY mileage DESC
LIMIT 1

To get the lowest value that is greater than or equal to a given search value do:

SELECT * FROM rates
WHERE mileage >= ?
ORDER BY mileage ASC
LIMIT 1

As far as doing the actual PDO you would do something like this:

$stmt = $dbh->prepare('SELECT * FROM rates WHERE mileage <= ? ORDER BY mileage DESC LIMIT 1');
$stmt->execute(array($term));
$row_object = $stmt->fetchObject();