PHP - Date Format Conversion

I have tried a large number of "solutions" to  this but everytime I use them I see 0000-00-00 in my date field instead of  the date even though I echoed and can see that the date looks correct.

Here's where I'm at:
I have a drop down for the month (1-12) and date fields (1-31) as well as a text input field for the year.  Using the POST array, I  have combined them into the xxxx-xx-xx format that I am using in my field as a date field in mysql. 

<code>
$date_value =$_POST['year'].'-'.$_POST['month'].'-'.$_POST['day'];
echo $date_value;
</code>

This outputs 2012-5-7 in my test echo but 0000-00-00 in the database.

I have tried unsuccessfully to use in a numberof suggested versions of:
strtotime()
mktime

Any help would be extremely appreciated.
I am aware that I need to validate this data and insure  that it is a valid date. That I'm okay with. I would like some help on getting it into the database.

Can someone tell me how to convert a MySQL date such as 2010-08-13 into the the US format, such as 8/13/2010, and also the reverse using PHP?  I can't seem to find the right functions.

Thanks!

I am working on a project where I need PHP and mysql to perform calculations on dates, so I am storing them in the mysql format 2011-09-12, I am writing a custom function that will convert this into a date('M d Y') format, but all I get when I run my function is "1" This is my first custom function, so i am sure it is a simple fix, I am just at the end of my spectrum on functions. I can do this as an inline script, but will need this on various pages
Code: [Select]
function readableDateConvert($mysqlTime) {
$phpTime = strtotime($mysqlTime);
$readableTime = date('M d Y',$newTime);
return $readableTime;
}

hey guys the date stored in mysql is yyyy-mm-dd i need to convert it to do a string compare i have used the following

$query = "SELECT * FROM booking where id=$sel"; 
            $result = mysql_query($query);
           while ($row = mysql_fetch_array($result))
           { $num1=$row['no_rooms'];
               $from1=$row['from'];
               $to=$row['to'];
               $sel1=$row['room_type'];
               $date = date('d-m-y', strtotime($from1)); 
             
              }
                 echo "$date";


it prints 01-01-70 can any1 tell me where is the error?

thanks

I am writing an app that takes ofx banking files files on convert them to csv for excel or importation into sql. I am on the last task. Converting the nonstandard date:time stamp. I am using preg_replace(). I am not the best at regular expressions. I am getting this error: "Warning: preg_replace() [function.preg-replace]: Unknown modifier '\' in C:\xampp\htdocs\banking\ofx-date.php on line 13"

CODE:
        // Date Time 20110228000600 (2011/02/28/, 00:06:00)
        // Expected Return '<DTPOSTED>2011/02/28,00:06:00'
       
        $ofxDate = '<DTPOSTED>20110228000600';
        $ofxNewDate =  substr($ofxDate,0,10) . substr($ofxDate,10,4) . '/' . substr($ofxDate,14,2) . '/' .
            substr($ofxDate,16,2) . ',' . substr($ofxDate,18,2) . ':' . substr($ofxDate,20,2) . ':' . substr($ofxDate,22,2);
        echo htmlentities($ofxNewDate) . PHP_EOL;;
       
        $patternA = '/<DTPOSTED>/\b[0-9]+\b';
        //$replacement = '/<DTPOSTED>/';
       
        $stringB = preg_replace($patternA, $ofxNewDate, ofxDate);
        echo htmlentities($StringB) . PHP_EOL;