Check whether the string is a unix timestamp

Question

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).

Answer 1

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}

Answer 2

As a unix timestamp is a integer, use is_int(). However as is_int() doesn't work on strings, we check if it is numeric and its intergal form is the same as its orignal form. Example:

( is_numeric($stamp) && (int)$stamp == $stamp )

Answer 3

I came across the same question and created the following solution for my self, where I don't have to mess with regular expressions or messy if-clauses:

/**
 * @param string $string
 * @return bool
 */
public function isTimestamp($string)
{
    try {
        new DateTime('@' . $string);
    } catch(Exception $e) {
        return false;
    }
    return true;
}

Answer 4

this looks like the way to go:

function is_timestamp($timestamp) {
    if(strtotime(date('d-m-Y H:i:s',$timestamp)) === (int)$timestamp) {
        return $timestamp;
    } else return false;
}

you could also add a is_numeric() check and all sort of other checks.
but this should/could be the basics.

Answer 5

Improved answer to @TD_Nijboer.

This will avoid an exception be thrown if the supplied string is not a time stamp:

function isTimestamp($timestamp) {
    if(ctype_digit($timestamp) && strtotime(date('Y-m-d H:i:s',$timestamp)) === (int)$timestamp) {
        return true;
    } else {
        return false;
}

Answer 6

This doesn't account for negative times(before 1970), nor does it account for extended ranges(you can use 64 bit integers so that a timestamp can represent a value far after 2038)

$valid = ctype_digit($str) && $str <= 2147483647;

Answer 7

You want to check if a string contains a high number?

is_numeric() is the key

Or convert it to DateTime and do some checks with it like an expected date range.

Answer 8

Another possibility:

$date_arg = time();
$date_is_ok = ($date_arg === strtotime(date('c', $date_arg)));

Answer 9

    //if anything else than digits inside the string then your string is no timestamp 
    //in which case maybe try to get the timestamp with strtotime

    if(preg_match('/[^\d]/', $str)) {
        $str = strtotime($str);

        if (false === $str) {
            //conversion failed - invalid time - invalid row
            return;
        }
    }

Answer 10

or

if ($startDate < strtotime('-30 years') || $startDate > strtotime('+30 years')) {
    //throw exception
}

Answer 11

If you might think to replace this solution with is_numeric(), please consider that php native function provides false positives for input strings like "1.1", "0123", "0xFF" which are not in timestamp format.