When working with PHP, you may need to choose between mutable and immutable PHP date objects. This guide explains the operation, shows what its arguments mean, and uses three separate examples to make the result easier to understand.
DateTimeImmutable vs DateTime: Choosing the Right Type: This topic combines several operations. The code demonstrates the important sequence and its effect.
What Is DateTimeImmutable vs DateTime: Choosing the Right Type in PHP?
Choose between mutable and immutable PHP date objects. This topic combines several operations. The code demonstrates the important sequence and its effect.
Syntax:
See the complete PHP example below.
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: DateTimeImmutable methods return replacements, so ignoring their return values discards the intended change.
Example 1: Basic Usage
This example introduces the operation with a short and predictable input.
<?php
$date = new DateTime("2026-01-01");
$date->modify("+1 day");
echo $date->format("Y-m-d");
Output:
2026-01-02
The code focuses on the main operation. This topic combines several operations. The code demonstrates the important sequence and its effect.
Example 2: Another Case
Now compare a different input, locale, date, or option to see another part of the behavior.
<?php
$date = new DateTimeImmutable("2026-01-01");
$newDate = $date->modify("+1 day");
echo $date->format("Y-m-d") . " / " . $newDate->format("Y-m-d");
Output:
2026-01-01 / 2026-01-02
What changes? DateTimeImmutable methods return replacements, so ignoring their return values discards the intended change.
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
function nextReview(DateTimeImmutable $createdAt): DateTimeImmutable {
return $createdAt->modify("+30 days");
}
$createdAt = new DateTimeImmutable("2026-02-01", new DateTimeZone("UTC"));
$reviewAt = nextReview($createdAt);
echo $createdAt->format("Y-m-d") . " / " . $reviewAt->format("Y-m-d");
Output:
2026-02-01 / 2026-03-03
The practical example demonstrates how to apply this operation to multiple values, a reusable task, or a validated input. This topic combines several operations. The code demonstrates the important sequence and its effect.
Important Behavior and Edge Cases
- Core behavior: This topic combines several operations. The code demonstrates the important sequence and its effect.
- Inputs and results: DateTimeImmutable methods return replacements, so ignoring their return values discards the intended change.
- Alternatives: Use DateTime for intentional in-place mutation and DateTimeImmutable for safer value-style behavior.
Comparison With Related Functions
| Function or Approach | When to Use It |
|---|---|
DateTimeImmutable vs DateTime: Choosing the Right Type | Choose between mutable and immutable php date objects. |
| Related PHP approach | Use DateTime for intentional in-place mutation and DateTimeImmutable for safer value-style behavior. |
Common Beginner Mistakes
| Mistake | Correct Approach |
|---|---|
| Using an incorrect input or option | DateTimeImmutable methods return replacements, so ignoring their return values discards the intended change. |
| Confusing this API with a related operation | Use DateTime for intentional in-place mutation and DateTimeImmutable for safer value-style behavior. |
| 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
- DateTimeImmutable vs DateTime: Choosing the Right Type helps you choose between mutable and immutable PHP date objects.
- This topic combines several operations. The code demonstrates the important sequence and its effect.
- DateTimeImmutable methods return replacements, so ignoring their return values discards the intended change.
Use DateTimeImmutable vs DateTime: Choosing the Right Type when you need to choose between mutable and immutable PHP date objects. 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.