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PHP get_declared_classes() Function: Usage and Examples

PHP get_declared_classes() Function: Usage and Examples: Lists class names currently declared in the process. See three examples and important limitations.

1 views Published Oct 17, 2026 Updated Oct 17, 2026 admin

The PHP get_declared_classes API performs a focused operation on an object or value. The examples below show its effect on actual data.

Lists class names currently declared in the process.

What Is get_declared_classes in PHP?


Lists class names currently declared in the process.

Syntax:

get_declared_classes(): array

This operation has no parameters.

Return type declared by PHP: array. The value or side effect is demonstrated in the examples below.

Example 1: Basic Usage


This example uses a small input to make the main behavior visible.

<?php

$classNames = get_declared_classes();
echo in_array(stdClass::class, $classNames, true) ? "available" : "missing";

Output:

available

Lists class names currently declared in the process.

Example 2: A Different Input


A different set of values shows the same operation in another situation.

<?php

$classNames = get_declared_classes();
echo in_array(stdClass::class, $classNames, true) ? "available" : "missing";
// The output reflects definitions in this PHP process.

Output:

available

The list depends on loaded extensions and previously included PHP files.

Practical Example: Applying the Feature


This example shows an application-style use of the feature, with its surrounding setup visible.

<?php

$classNames = get_declared_classes();
echo in_array(stdClass::class, $classNames, true) ? "available" : "missing";
// Use this result while deciding how to handle optional application features.

Output:

available

The code is shown for learning. Adjust the class names, inputs and error handling to suit your application.

Important Behavior and Edge Cases


  • The list depends on loaded extensions and previously included PHP files.
  • Lists class names currently declared in the process.
  • Observe differences in empty inputs, invalid states and optional extension availability where relevant.

Comparison With Related Approaches


ApproachImportant Difference
get_declared_classesLists class names currently declared in the process.
class_exists()get_declared_classes() enumerates loaded classes; class_exists() probes a single name.

Common Beginner Mistakes


MistakeCorrect Approach
Ignoring the documented state or precondition of get_declared_classesThe list depends on loaded extensions and previously included PHP files.
Expecting a different type of resultRead the declared return type and distinguish returned values from changes to the source object.
Assuming a related API works identicallyget_declared_classes() enumerates loaded classes; class_exists() probes a single name.

Key Takeaways


  • Lists class names currently declared in the process.
  • The list depends on loaded extensions and previously included PHP files.
  • Use the example that matches the values, runtime version and dependencies in your application.

get_declared_classes is useful when its behavior matches the data structure and lifecycle of your PHP application. Choose it with a clear understanding of its preconditions and returned values.

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