31082016

dd-mm-yyyy

echo "<br/><hr/>" . $fechaIn . "<hr/><br/>";
echo "<br/><hr/>" . date('d-m-Y', $fechaIn) . "<hr/><br/>";

$fechaIn = '31082016';

$y = substr( $fechaIn, 4, 4 );
$m = substr( $fechaIn, 2, 2 );
$d = substr( $fechaIn, 0, 2 );

echo "<br/><hr/>" . $fechaIn . "<hr/><br/>";
echo "<br/><hr/>" . date( 'd-m-Y', mktime( 0, 0, 0, $m, $d, $y ) ) . "<hr/><br/>";

31-08-2016

<?php
$source = '2012-07-31';
$date = new DateTime($source);
echo $date->format('d.m.Y'); // 31.07.2012
echo $date->format('d-m-Y'); // 31-07-2012
?>

date("d/m/Y", strtotime($str));

$var = '20/04/2012';
$date = str_replace('/', '-', $var);
echo date('Y-m-d', strtotime($date));