When working with PHP, you may need to create a date-time value that cannot be modified in place. This guide explains the operation, shows what its arguments mean, and uses three separate examples to make the result easier to understand.
date_create_immutable: Adjustment methods return a new DateTimeImmutable and preserve the original.
What Is date_create_immutable in PHP?
Create a date-time value that cannot be modified in place. Adjustment methods return a new DateTimeImmutable and preserve the original.
Syntax:
date_create_immutable(string $datetime = "now", ?DateTimeZone $timezone = null): DateTimeImmutable|false
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: Always use the returned value after modifying an immutable date.
Example 1: Basic Usage
This example introduces the operation with a short and predictable input.
<?php
$date = date_create_immutable("2026-10-16", new DateTimeZone("UTC"));
echo $date->format("Y-m-d");
Output:
2026-10-16
The code focuses on the main operation. Adjustment methods return a new DateTimeImmutable and preserve the original.
Example 2: Another Case
Now compare a different input, locale, date, or option to see another part of the behavior.
<?php
$date = date_create_immutable("2026-10-16", new DateTimeZone("UTC"));
echo $date->modify("+3 days")->format("Y-m-d");
Output:
2026-10-19
What changes? Always use the returned value after modifying an immutable date.
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
$createdAt = date_create_immutable("2026-06-01", new DateTimeZone("UTC"));
$expiresAt = $createdAt->modify("+30 days");
echo $createdAt->format("Y-m-d") . " to " . $expiresAt->format("Y-m-d");
Output:
2026-06-01 to 2026-07-01
The practical example demonstrates how to apply this operation to multiple values, a reusable task, or a validated input. Adjustment methods return a new DateTimeImmutable and preserve the original.
Important Behavior and Edge Cases
- Core behavior: Adjustment methods return a new DateTimeImmutable and preserve the original.
- Inputs and results: Always use the returned value after modifying an immutable date.
- Alternatives: date_create() creates mutable DateTime objects.
Comparison With Related Functions
| Function or Approach | When to Use It |
|---|---|
date_create_immutable | Create a date-time value that cannot be modified in place. |
| Related PHP approach | date_create() creates mutable DateTime objects. |
Common Beginner Mistakes
| Mistake | Correct Approach |
|---|---|
| Using an incorrect input or option | Always use the returned value after modifying an immutable date. |
| Confusing this API with a related operation | date_create() creates mutable DateTime objects. |
| 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
- date_create_immutable helps you create a date-time value that cannot be modified in place.
- Adjustment methods return a new DateTimeImmutable and preserve the original.
- Always use the returned value after modifying an immutable date.
Use date_create_immutable when you need to create a date-time value that cannot be modified in place. 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.