How to merge 2 objects in PHP

Introduction

Merging objects in PHP is a common operation that comes in handy when dealing with data manipulation and object-oriented programming. It allows developers to combine the properties of two objects into a single object, which can be beneficial when integrating data from multiple sources, extending objects, or simply organizing data more effectively.

What is Object Merging?

Object merging is the process of taking properties from one or more objects and combining them into a single, new object. The resulting object contains the properties and values from all the original objects.

Using the array_merge Function

While array_merge is typically used for arrays, it can also be employed to merge objects by first converting them to arrays:

$object1 = (object)[ 'name' => 'John', 'age' => 25 ];
$object2 = (object)[ 'address' => '123 Main St', 'city' => 'Anytown' ];

$mergedArray = array_merge((array)$object1, (array)$object2);
$mergedObject = (object)$mergedArray;

This approach is straightforward but has its limitations, as array_merge doesn’t handle nested arrays or recursive merging.

Using the stdClass for Merging

Objects can be merged by creating a new stdClass object and then setting the properties manually:

$object1 = new stdClass;
$object1->name = 'John';
$object1->age = 25;

$object2 = new stdClass;
$object2->address = '123 Main St';
$object2->city = 'Anytown';

$mergedObject = new stdClass;
foreach($object1 as $property => $value) {
    $mergedObject->$property = $value;
}
foreach($object2 as $property => $value) {
    if (!isset($mergedObject->$property)) {
        $mergedObject->$property = $value;
    }
}

The disadvantage of this manual approach is that it doesn’t automatically handle property conflicts or deep merging.

Custom Object Merging Functions

For complex merging requirements, including handling conflicts, recursive merging, or merging objects with private and protected properties, it may necessay to create custom merge functions:

function mergeObjects($object1, $object2) {
    $result = new stdClass;
    foreach (new ReflectionObject($object1) as $property => $value) {
        $property->setAccessible(true);
        $result->$property = $property->getValue($object1);
        $property->setAccessible(false);
    }
    foreach (new ReflectionObject($object2) as $property => $value) {
        $property->setAccessible(true);
        $result->$property = $property->getValue($object2);
        $property->setAccessible(false);
    }
    return $result;
}

A custom merge function can also be written to handle nested objects and perform deep merges.

Using third-party libraries for Object Merging

Third-party libraries often offer more advanced and convenient object merging functionalities. Libraries like Lodash provide flexible and powerful ways to merge objects, including options to handle property conflicts, perform deep merges, and work with complex data structures.

Best Practices

When merging objects, it is important to consider the following best practices to ensure that the integrity and structure of the data is maintained:

• Be mindful of the property conflicts and have a strategy for resolution.
• Understand and leverage differences between shallow and deep merging based on your use case.
• Consider the impact of merging on inheritance and prototype chains.
• Use existing, well-tested libraries when available to ensure robustness and save development time.

Conclusion

Merging objects in PHP can be done in a number of ways, each with its own use cases, advantages, and limitations. From utilizing built-in PHP functions to making use of advanced third-party libraries, it’s essential to choose the right approach according to your specific needs. In this guide, we have covered the fundamental techniques and looked at how to handle more complex scenarios, providing you with the tools needed to effectively merge objects in PHP.