converting dd/mm/yyyy into yyyy/mm/dd using php and sql

i'm quite new with php. i think this is quite straight forward but i'm confused.

i have a form which asks users for a date of their choice, the format they enter is dd/mm/yyyy

the linked mysql database is formatted yyyy/mm/dd, from what i understand you can't change this.

i'm just trying to figure out where i can change the format of the date. would it be in the sql line that sends the information?

i found this unrelated answer:

<?php 
$date = date("Y-m-d"); 
mysql_query("INSERT INTO date_table VALUES ('$name', '$date')", $db_connection); 
?>

but i can't get this to work...

here are some snippets of the code i currently have:

// Check for night attending:
    if (empty($_POST['night_attending'])) {
        $errors[] = 'You forgot to enter the night you want to attend.';
    } else {
        $na = mysqli_real_escape_string($dbc, trim($_POST['night_attending']));
    }

.................开发者_开发技巧....................

// Make the query:
        $q = "INSERT INTO guests (first_name, last_name, email, night_attending) VALUES ('$fn', '$ln', '$e', '$na')";       
        $r = @mysqli_query ($dbc, $q); // Run the query.
        if ($r) { // If it ran OK.

.....................................

<p>Night Attending: <input type="text"id="datepicker"  name="night_attending" size="10" value="<?php if (isset($_POST['night_attending'])) echo $_POST['night_attending']; ?>" /></p>

thanks for your time guys.

alastair

Update: (Based On Comments)

To get the date value from your form, you can do this:

$date = date('Y/m/d', strtotime($_POST['night_attending']));

Where it is assumed that:

• The data received is in valid format
• You are using POST method in your <form> tag or change accordingly.

You need to use strtotime:

$date = date('Y/m/d', strtotime($date));

I usually use this code, to convert dd/mm/yyyy into yyyy/mm/dd:

$convert = 'dd/mm/yyyy';
$converted = implode(/, array_reverse(explode(/, $convert)));

I know that there are some built-in functions to do it, but I think that by this way it's more customizable.