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Diese Funktion ist ein Alias für: DateTime::__construct()
An interesting note that came from the tutorial (as well as my own testing) is that the DateTime constructor is exception happy. In other languages this is a bit of a no-no - throwing exceptions from within a constructor can cause all sorts of odd problems!
Either way, because of this you should attempt to catch any exception and only use the object if it does not throw an exception.
<?php
$bad_date_string = 'ublingah!';
try {
$dt = new DateTime($bad_date_string);
}
catch(Exception $e) {
// catches 'Failed to parse time string (ublingah!) at position 0 (u)' exception.
// don't use this object
}
?>
Looks like the DateTime class does not exist in my PHP 5.1.5 installation. The only documentation I can find says this class shows up in PHP 5.2
Serialization and unserialization fail for the DateTime object (PHP 5.2.5).
With your own __sleep and __wakeup function in a child class you can work around this problem.
<?php
class MyDateTime extends DateTime {
private $_str;
public function __sleep(){
$this->_str = $this->format('c');
return array('_str');
}
public function __wakeup() {
$this->__construct($this->_str);
}
}
?>
Regards, Mick
[Ed. Please be aware that this is *not* 100% correct as you lose the timezone information. Always use the standard serialization if it's available!]
The string format here is a bit wrong, yes it accepts the same format, but not the same range as strtotime.
strtotime can't handle dates like 2100-01-01 while this one can..
When using these functions inside of destructors or functions called as a result of being registered with register_shutdown_handler, be sure to use date_create() instead of new DateTime(). This is because new DateTime will throw an exception on failure, which is not permitted in any of the above circumstances. If new DateTime() does fail in one of these circumstances, you will get an error stating "Fatal error: Exception thrown without a stack frame in Unknown on line 0."
The manual says "Returns DateTime object on success or FALSE on failure".
I tried hard to provoke a failure, but I seem to always get a DateTime object back, even though the PHP log says things like: "Failed to parse time string (2007W992-11:16:47+00:00) at position 5 (9): Unexpected character"
So if you (need to) check the result, beware!
[red. in PHP 5.3 and higher, you can do that with DateTime::getLastErrors().]
If you want to create the DateTime object directly from a timestamp use this
<?php
$st = 1170288000 // a timestamp
$dt = new DateTime("@$st");
?>
See also: http://bugs.php.net/bug.php?id=40171
"String in a format accepted by strtotime()" is not 100% truth - you cannot pass timezone info in the string used as DateTime constructor, while you can do it with strtotime(). It may be a problem if you would like to create a date from GMT time and then display it in your local timezone, for example:
<?php
$timeZone = 'Europe/Warsaw'; // +2 hours
date_default_timezone_set($timeZone);
$dateSrc = '2007-04-19 12:50 GMT';
$dateTime = new DateTime($dateSrc);
echo 'date(): '.date('H:i:s', strtotime($dateSrc));
// correct! date(): 14:50:00
echo 'DateTime::format(): '.$dateTime->format('H:i:s');
// INCORRECT! DateTime::format(): 12:50:00
?>
[red. your claim that "is not 100% truth" is incorrect, you're seeing desired behavior here. The timezone passed as 2nd argument is used as a default fall back, in case the parsed string doesn't provide TZ information.]
So if you want to convert date between different timezones, you have to create two DateTimeZone objects - one for the input and one for output, like this:
<?php
$timeZone = 'Europe/Warsaw'; // +2 hours
$dateSrc = '2007-04-19 12:50';
$dateTime = new DateTime($dateSrc, new DateTimeZone('GMT'));
$dateTime->setTimeZone(new DateTimeZone($timeZone));
echo 'DateTime::format(): '.$dateTime->format('H:i:s');
// CORRECT! DateTime::format(): 14:50:00
?>
I'm not sure if this is a bug or desired behaviour.
[red. you don't have to do create two DateTimeZone objects, this works too:
<?php
$timeZone = 'Europe/Warsaw'; // +2 hours
$dateSrc = '2007-04-19 12:50 GMT';
$dateTime = new DateTime($dateSrc);
$dateTime->setTimeZone(new DateTimeZone($timeZone));
echo 'DateTime::format(): '.$dateTime->format('H:i:s');
// CORRECT! DateTime::format(): 14:50:00
?>
]
date_create and other DateTime related functions are included by default only in PHP versions equal and greater than 5.2.
In PHP 5.1.2 this functionality is marked to be experimental and has to be enabled at compile time.
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