new.dateInterval

Code example

<?php declare(strict_types = 1);

new DateInterval('1M');

Why is it reported?

The duration string passed to the DateInterval constructor is invalid and produces an error at runtime. PHP's DateInterval constructor expects an ISO 8601 duration string starting with the letter P.

In the example above, '1M' is missing the required P prefix. The correct form is 'P1M' for one month or 'PT1M' for one minute.

How to fix it

Use a valid ISO 8601 duration format:

-new DateInterval('1M');
+new DateInterval('P1M');

Valid duration strings always start with P and follow this structure:

• 'P1Y' — 1 year
• 'P1M' — 1 month
• 'P1D' — 1 day
• 'PT1H' — 1 hour
• 'PT1M' — 1 minute
• 'PT1S' — 1 second
• 'P1Y2M3DT4H5M6S' — combined duration

The T separator is required before time components (hours, minutes, seconds).