When a PHP application needs to reads format information from a date-time value, choosing the right API and checking its results helps keep code understandable and dependable. This guide explains DateTimeImmutable::format with focused examples and important details.
What Is DateTimeImmutable::format in PHP?
DateTimeImmutable::format reads format information from a date-time value. getOffset() is measured in seconds; getTimestamp() is seconds since the Unix epoch; getMicrosecond() returns the fractional seconds component.
Syntax:
DateTimeImmutable::format(format) : stringParameters and return value: Parameters: <required> string $format. Check the return value or modified object rather than assuming the operation always succeeds.
Important: Use explicit IANA time zones in production and account for daylight-saving changes when calculating local schedules.
Example 1: Basic Usage
Start with a compact input so the main operation is visible.
<?php
$appointment = new DateTimeImmutable("2026-03-14 09:30:15.123456", new DateTimeZone("Europe/London"));
echo $appointment->format("l, d M Y H:i");
Output:
Saturday, 14 Mar 2026 09:30Reads format information from a date-time value. getOffset() is measured in seconds; getTimestamp() is seconds since the Unix epoch; getMicrosecond() returns the fractional seconds component.
Example 2: A Different Input
The next example changes the input or option to illustrate another behavior.
<?php
$appointment = new DateTimeImmutable("2026-07-01 14:20:30.654321", new DateTimeZone("Asia/Tokyo"));
echo $appointment->format("l, d M Y H:i");
Output:
Wednesday, 01 Jul 2026 14:20Compare this result with the first example. getOffset() is measured in seconds; getTimestamp() is seconds since the Unix epoch; getMicrosecond() returns the fractional seconds component.
Practical Example: Applying the Function
This example combines the API with a realistic processing step and shows where to check its result.
<?php
$appointments = ["2026-01-10 08:15:00", "2026-02-12 16:30:00"];
foreach ($appointments as $value) {
$appointment = new DateTimeImmutable($value, new DateTimeZone("UTC"));
echo $appointment->format("l, d M Y H:i") . PHP_EOL;
}
Output:
Saturday, 10 Jan 2026 08:15
Thursday, 12 Feb 2026 16:30Adapt the inputs to your application and validate the output before storing or displaying it. getOffset() is measured in seconds; getTimestamp() is seconds since the Unix epoch; getMicrosecond() returns the fractional seconds component.
Important Behavior and Edge Cases
- Main purpose: Reads format information from a date-time value.
- Errors and boundaries: getOffset() is measured in seconds; getTimestamp() is seconds since the Unix epoch; getMicrosecond() returns the fractional seconds component.
- Environment: Use explicit IANA time zones in production and account for daylight-saving changes when calculating local schedules.
Comparison With Related Functions
| Function or Approach | When to Use It |
|---|---|
DateTimeImmutable::format | Reads format information from a date-time value. |
| DateTimeInterface | Consider this alternative when you need different behavior or a different abstraction. |
Common Beginner Mistakes
| Mistake | Correct Approach |
|---|---|
| Assuming the operation succeeds for every input | getOffset() is measured in seconds; getTimestamp() is seconds since the Unix epoch; getMicrosecond() returns the fractional seconds component. |
| Ignoring runtime requirements or variable output | Use explicit IANA time zones in production and account for daylight-saving changes when calculating local schedules. |
| Using the wrong API for the goal | Compare DateTimeImmutable::format with DateTimeInterface before selecting an approach. |
Key Takeaways
- Reads format information from a date-time value.
- getOffset() is measured in seconds; getTimestamp() is seconds since the Unix epoch; getMicrosecond() returns the fractional seconds component.
- Use explicit IANA time zones in production and account for daylight-saving changes when calculating local schedules.
Use DateTimeImmutable::format when you need to reads format information from a date-time value. The three examples move from a simple call to a practical use. Validate all external input and handle failures explicitly.