日期比较PHP Mysql

Question

I have a system that is comparing mysql tabled dates with today's date to see whether a certain document needs to be renewed:

<?php
        $student_id = $row_student['student_id'];

        $query_ieps = mysql_query("SELECT * FROM `iep` WHERE student_id = ".$student_id."") or die(mysql_error());

        $iep_count = mysql_num_rows($query_ieps);

        $row_iep = mysql_fetch_assoc($query_ieps);

        $today = date("d-m-Y");

        $iep_date = $row_iep['iep_renewal'];

        $convert_iep_date = date("d-m-Y", strtotime($iep_date));

        $redate_coverted_date = $convert_iep_date; 

        if($iep_count == 0){ $iep_status = "No IEP on record"; $iep_td_status = "grey-alert"; }
        elseif($today <= $redate_coverted_date) { $iep_status = "Due for Renewal"; $iep_td_status = "mid-alert"; }
        elseif($today >= $redate_coverted_date) { $iep_status = "Up to Date"; $iep_td_status = "green-alert"; };
?>

I have two sets of values:

id: 1 -> iep_renewal: 12-02-2012

id: 2 -> iep_renewal: 12-08-2012

However the table outputs that both these values are "Up to Date" when the first is clearly not.

Is there a way to do this at all and if so how!

Answer 1

$some_date_timestamp = strtotime('18-02-2011');

$current_timestamp = time();

echo ($some_date_timestamp < $current_timestamp) ? 'Old date' : 'Future date';

Answer 2

$today = 19-02-2012 (today's date) and $redate_converted_date = 12-02-2012 (date from DB)

You can't compare dates in that format: They'll be compared as strings, not dates, leading to incorrect results.

Use strtotime() or DateTime to convert them into timestamps (or DateTime objects) which you can compare.

Answer 3

As another possibility, you can export as a unix time stamp straight out of the DB by wrapping it in a function like this:

SELECT *, UNIX_TIMESTAMP(`iep_renewal`) AS iep_renewal_unix

There may be performance issues associated with wrapping columns in functions on large data sets.