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I have a string and I need to find out whether it is a unix timestamp or not, how can I do that effectively?

I found this thread via Google, but it doesn't come up with a very solid answer, I'm afraid. (And yes, I cribbed the question from the original poster on the aforementioned thread).



Ok, after fiddling with this for some time, I withdraw the solution with date('U') and suggest to use this one instead:

function isValidTimeStamp($timestamp)
    return ((string) (int) $timestamp === $timestamp) 
        && ($timestamp <= PHP_INT_MAX)
        && ($timestamp >= ~PHP_INT_MAX);

This check will only return true if the given $timestamp is a string and consists solely of digits and an optional minus character. The number also has to be within the bit range of an integer (EDIT: actually unneeded as shown here).

var_dump( isValidTimeStamp(1)             ); // false
var_dump( isValidTimeStamp('1')           ); // TRUE
var_dump( isValidTimeStamp('1.0')         ); // false
var_dump( isValidTimeStamp('1.1')         ); // false
var_dump( isValidTimeStamp('0xFF')        ); // false
var_dump( isValidTimeStamp('0123')        ); // false
var_dump( isValidTimeStamp('01090')       ); // false
var_dump( isValidTimeStamp('-1000000')    ); // TRUE
var_dump( isValidTimeStamp('+1000000')    ); // false
var_dump( isValidTimeStamp('2147483648')  ); // false
var_dump( isValidTimeStamp('-2147483649') ); // false

The check for PHP_INT_MAX is to ensure that your string can be used correctly by date and the likes, e.g. it ensures this doesn't happen*:

echo date('Y-m-d', '2147483648');  // 1901-12-13
echo date('Y-m-d', '-2147483649'); // 2038-01-19

On 64bit systems the integer is of course larger than that and the function will no longer return false for "2147483648" and "-2147483649" but for the corresponding larger numbers.

(*) Note: I'm not 100% sure, the bit range corresponds with what date can use though

Thursday, September 29, 2022

Your date format is wrong... i is for minute, not m (months).

return date("Y-m-d H:i:s", $unixTimestamp);

A few side notes:

  • There's no need to re-assign, i.e. $unixTimestamp = $unixTimestamp;
  • Since you're using PHP > 5.3. you may be interested in the new DateTime object.
Saturday, August 13, 2022

You can initialise a Date object and call getTime() to get it in unix form. It comes out in milliseconds so you'll need to divide by 1000 to get it in seconds.

(new Date("2013/09/05 15:34:00").getTime()/1000)

It may have decimal bits so wrapping it in Math.round would clean that.

Math.round(new Date("2013/09/05 15:34:00").getTime()/1000)
Monday, October 17, 2022

As Peter Halasz mentions in T-SQL DateTime to Unix Timestamp:

Converting a datetime to unix timestamp is easy, but involves error prone typing the following:

@timestamp=DATEDIFF(second,{d '1970-01-01'},@datetime)

Where @datetime is the datetime value you want to convert. The {d ‘yyyy-mm-dd’} notation is an ODBC escape sequence.

The function:

@ctimestamp datetime
RETURNS integer
  /* Function body */
  declare @return integer
  SELECT @return = DATEDIFF(SECOND,{d '1970-01-01'}, @ctimestamp)
  return @return

Try it out now like below @O A:

Monday, September 5, 2022

You can use date() function

$weekday = date('N', $timestamp); // 1-7
$month = date('m', $timestamp); // 1-12
$day = date('d', $timestamp); // 1-31
Wednesday, October 19, 2022
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