Time and Date difference using a PHP function

This is a simple PHP function dateTimeDiff() written for an application that I am developing, useful to get time and date difference between two date (a reference date and "now"), with a Digg-like style (ex: 12 min 20 sec ago). The mask of reference for each date is 2007-10-18 20:05:22, a standard MySQL datetime field.

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How it works?
First, you have to include the file timeFunction.php into the PHP file that will use the function.

<?php include('timeFunction.php') ?>

... and you have to pass the data which it goes made the comparison:

dateTimeDiff($dataRef);

... where $dataRef is, for example, a value from a SQL query.


The code
This is the code of dateTimeDiff() PHP function:

<?php function dateTimeDiff($data_ref){

// Get the current date
$current_date = date('Y-m-d H:i:s');

// Extract from $current_date
$current_year = substr($current_date,0,4);
$current_month = substr($current_date,5,2);
$current_day = substr($current_date,8,2);

// Extract from $data_ref
$ref_year = substr($data_ref,0,4);
$ref_month = substr($data_ref,5,2);
$ref_day = substr($data_ref,8,2);

// create a string yyyymmdd 20071021
$tempMaxDate = $current_year . $current_month . $current_day;
$tempDataRef = $ref_year . $ref_month . $ref_day;

$tempDifference = $tempMaxDate-$tempDataRef;

// If the difference is GT 10 days show the date
if($tempDifference >= 10){
echo $data_ref;
} else {

// Extract $current_date H:m:ss
$current_hour = substr($current_date,11,2);
$current_min = substr($current_date,14,2);
$current_seconds = substr($current_date,17,2);

// Extract $data_ref Date H:m:ss
$ref_hour = substr($data_ref,11,2);
$ref_min = substr($data_ref,14,2);
$ref_seconds = substr($data_ref,17,2);

$hDf = $current_hour-$ref_hour;
$mDf = $current_min-$ref_min;
$sDf = $current_seconds-$ref_seconds;

// Show time difference ex: 2 min 54 sec ago.
if($dDf<1){
if($hDf>0){
if($mDf<0){
$mDf = 60 + $mDf;
$hDf = $hDf - 1;
echo $mDf . ' min ago';
} else {
echo $hDf. ' hr ' . $mDf . ' min ago';
}
} else {
if($mDf>0){
echo $mDf . ' min ' . $sDf . ' sec ago';
} else {
echo $sDf . ' sec ago';
}
}
} else {
echo $dDf . ' days ago';
}
?>