DateInterval::createFromDateString ( string $time )
When the manual says "Uses the normal date parsers" it means that this function cannot take $time = ISO8601 strings like "P7D". If you want to use those, you must use the constructor.
(PHP 5 >= 5.3.0, PHP 7)
DateInterval::createFromDateString — Sets up a DateInterval from the relative parts of the string
Uses the normal date parsers and sets up a DateInterval from the relative parts of the parsed string.
datetime
A date with relative parts. Specifically, the relative formats supported by the parser used for strtotime() and DateTime will be used to construct the DateInterval.
Example #1 Parsing valid date intervals
<?php
// Each set of intervals is equal.
$i = new DateInterval('P1D');
$i = DateInterval::createFromDateString('1 day');
$i = new DateInterval('P2W');
$i = DateInterval::createFromDateString('2 weeks');
$i = new DateInterval('P3M');
$i = DateInterval::createFromDateString('3 months');
$i = new DateInterval('P4Y');
$i = DateInterval::createFromDateString('4 years');
$i = new DateInterval('P1Y1D');
$i = DateInterval::createFromDateString('1 year + 1 day');
$i = new DateInterval('P1DT12H');
$i = DateInterval::createFromDateString('1 day + 12 hours');
$i = new DateInterval('PT3600S');
$i = DateInterval::createFromDateString('3600 seconds');
?>
Returns a new DateInterval instance on success, sau false
în cazul eșecului.