When working with PHP, you may need to render the components of a DateInterval as text. This guide explains the operation, shows what its arguments mean, and uses three separate examples to make the result easier to understand.
DateInterval::format: This formatter uses percent-prefixed directives rather than date() format characters.
What Is DateInterval::format in PHP?
Render the components of a DateInterval as text. This formatter uses percent-prefixed directives rather than date() format characters.
Syntax:
$interval->format(string $format): string
Parameters and return value: The signature above identifies the arguments and return type where the API has a single call. For topic guides, follow the sequence of calls in the examples. Always distinguish a returned value from an object or variable modified by reference.
Important: %a may be unavailable for intervals created without computing a date difference; it is not interchangeable with %d.
Example 1: Basic Usage
This example introduces the operation with a short and predictable input.
<?php
$interval = new DateInterval("P2DT4H");
echo $interval->format("%d days, %h hours");
Output:
2 days, 4 hours
The code focuses on the main operation. This formatter uses percent-prefixed directives rather than date() format characters.
Example 2: Another Case
Now compare a different input, locale, date, or option to see another part of the behavior.
<?php
$start = new DateTimeImmutable("2026-01-01");
$end = new DateTimeImmutable("2026-01-10");
echo $start->diff($end)->format("%a total days");
Output:
9 total days
What changes? %a may be unavailable for intervals created without computing a date difference; it is not interchangeable with %d.
Practical Example: Applying It in an Application
Use the following separate example as a starting point for a small application task. Check any extension or environment requirements below before running it.
<?php
$intervals = [new DateInterval("P1D"), new DateInterval("P3DT2H")];
foreach ($intervals as $interval) {
echo $interval->format("%d days, %h hours") . PHP_EOL;
}
Output:
1 days, 0 hours
3 days, 2 hours
The practical example demonstrates how to apply this operation to multiple values, a reusable task, or a validated input. This formatter uses percent-prefixed directives rather than date() format characters.
Important Behavior and Edge Cases
- Core behavior: This formatter uses percent-prefixed directives rather than date() format characters.
- Inputs and results: %a may be unavailable for intervals created without computing a date difference; it is not interchangeable with %d.
- Alternatives: date_interval_format() provides the procedural equivalent.
Comparison With Related Functions
| Function or Approach | When to Use It |
|---|---|
DateInterval::format | Render the components of a dateinterval as text. |
| Related PHP approach | date_interval_format() provides the procedural equivalent. |
Common Beginner Mistakes
| Mistake | Correct Approach |
|---|---|
| Using an incorrect input or option | %a may be unavailable for intervals created without computing a date difference; it is not interchangeable with %d. |
| Confusing this API with a related operation | date_interval_format() provides the procedural equivalent. |
| Assuming output is identical across environments | Check return values and required extensions or versions. Use explicit locale, timezone or encoding settings when they affect the result. |
Key Takeaways
- DateInterval::format helps you render the components of a DateInterval as text.
- This formatter uses percent-prefixed directives rather than date() format characters.
- %a may be unavailable for intervals created without computing a date difference; it is not interchangeable with %d.
Use DateInterval::format when you need to render the components of a DateInterval as text. Start with the first example, compare the second, and adapt the practical example to your inputs. Confirm the return value and environment requirements before adding it to production code.