I have tried to solve it by extracting the numeric part and then parsed it using date function. But it shows me some old date which I guess is not correct.
$datef = "1490914800000+0100";
$adada = date('Y-m-d H:i:s', $datef);
// Gives date 1987-10-13 18:31:28 which is an old date. Please suggest.
One approach, well-covered by this SO question, is to use the DateTime() function to convert time in seconds since epoch to a date, and then display this date using format(). But there are two caveats with your data. First, you appear to have milliseconds since the epoch, which needs to be converted to seconds. Second, you also have a timezone shift, in hours, tagged to the end. I split your $datef string into two parts, epoch and timezone, then arrive at the number of seconds since epoch.
list($epoch, $timezone) = explode('+', $datef);
$epoch = ($epoch / 1000) + (substr($timezone, 0, 2)*60*60) +
(substr($timezone, 2, 2)*60);
$dt = new DateTime("@$epoch");
echo $dt->format('Y-m-d H:i:s');
Output:
2017-03-31 00:00:00
Demo here:
The time seems to be in milliseconds. You can add the timezone shift to the seconds. 1 hour = 3600 seconds.
$milliSeconds = intval("1490914800000");
$seconds = $milliSeconds/1000;
$date = date("Y-m-d H:i:s", $seconds);