PHP validate ISO 8601 date string

Question

How do you validate ISO 8601 date string (ex: 2011-10-02T23:25:42Z).

I know that there are several possible representations of ISO 8601 dates, but I\'m only interest

Answer 1

I want to share my lightweight solution. It is not ideal, but might be helpful for someone.

function validISO8601Date($value)
{
    if (!is_string($value)) {
        return false;
    }

    $dateTime = \DateTime::createFromFormat(\DateTime::ISO8601, $value);

    if ($dateTime) {
        return $dateTime->format(\DateTime::ISO8601) === $value;
    }

    return false;
}

Atention!

Some valid ISO8601 dates will fail Look at the list below

NOT VALID  --> '' // Correct
NOT VALID  --> 'string' // Correct
VALID      --> '2000-01-01T01:00:00+1200' // This is the only format function returns as valid
NOT VALID  --> '2015-01 first' // Correct
NOT VALID  --> '2000-01-01T01:00:00Z' // Must be valid!
NOT VALID  --> '2000-01-01T01:00:00+01' // Must be valid!