Check Whether the String Is a Unix Timestamp

Check whether the string is a unix timestamp

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.

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

Checking if am receiving a valid unix timestamp

I'd recommend Moment.js for everything date related in JS

Especially the isValid() method is of interest

console.log("12-12-1212", moment("12-12-1212", 'YYYY-MM-DD', true).format(), moment("12-12-1212", 'YYYY-MM-DD', true).isValid())
console.log("1212-12-12", moment("1212-12-12", 'YYYY-MM-DD', true).format(), moment("1212-12-12", 'YYYY-MM-DD', true).isValid())
console.log("1212-12-1212", moment("1212-12-1212", 'YYYY-MM-DD', true).format(), moment("1212-12-1212", 'YYYY-MM-DD', true).isValid())
console.log('1318874398', moment('1318874398', 'X', true).format(), moment('1318874398', 'X', true).isValid())

<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.27.0/moment.min.js"></script>

$var is valid unix timestamp

Here, the first should be TRUE and the second should be FALSE

Why? 20101108 is a valid UNIX timestamp, - as you say, it's August 21, 1970. Could well be a person's birthday for example.

The only way to achieve what you want is to set a range of dates that mark a "sane" timestamp by the definition you are working with - e.g. anything after January 1st, 2000 - and do a check against that.

JestJS: How to test for unix timestamp

First, be sure you use \d in your regex to match digits, not d which only matches the actual letter.

If that doesn't solve the issue, convert the value to a string:

expect(1509736771.toString()).toMatch(/^\d{10}$/)

or

expect('' + 1509736771).toMatch(/^\d{10}$/)

How to identify a unix timestamp from a date?

Maybe naive, but a solution might be to check if $data has a numeric value.

if (is_numeric($data)) { // it's a timestamp   
    $data =  date("d-m-Y H:i:s", (int) $data);
}

strtotime and checking if valid timestamp

'Cause strtotime returns int and you are comparing it strictly with string. Change this (string) (int) $timestamp === $timestamp to this (int)(string) $timestamp === $timestamp

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