PHP array_merge() vs array_combine() – Difference & Examples

Introduction

When developers need to combine or merge arrays. PHP provides several built-in functions to perform these operations. Two important functions used for combining arrays are:

1. array_merge() is used to merge two or more arrays together.
2. array_combine() is used to create a new array using one array as keys and another array as values.

Understanding the difference between array_merge() vs array_combine() helps developers manage arrays more effectively.

What is array_merge() in PHP?

The array_merge() function is used to merge two or more arrays into a single array.

When arrays are merged:

• Values from all arrays are added to one array.
• Numeric keys are reindexed automatically.
• If there are duplicate string keys, the later value overwrites the previous value.

Syntax of array_merge()

Parameters

• array1 – The first array
• array2 – The second array
• Additional arrays can also be added

Example of array_merge()

$array1 = array("PHP", "Java");
$array2 = array("Python", "JavaScript");
$result = array_merge($array1, $array2);
print_r($result);

Output

Explanation

In this example:

1. Two arrays are created.
2. The array_merge() function combines them into one array.
3. The elements are placed sequentially.

array_merge() with Associative Arrays

When associative arrays are merged, duplicate keys are replaced by the latest value.

$array1 = array("name" => "Rahul", "age" => 20);
$array2 = array("age" => 25, "city" => "Delhi");
$result = array_merge($array1, $array2);
print_r($result);

Output

Explanation

Here:

• Both arrays contain the key age.
• The value 25 replaces 20.

What is array_combine() in PHP?

The array_combine() function is used to create a new array by combining two arrays.

• The first array becomes the keys
• The second array becomes the values

Both arrays must contain the same number of elements, otherwise PHP will generate an error.

Syntax of array_combine()

array_combine(keys, values);

Parameters

• keys – Array containing keys
• values – Array containing values

Example of array_combine()

$keys = array("name", "age", "city");
$values = array("Ravi", 22, "Mumbai");
$result = array_combine($keys, $values);
print_r($result);

Output

Explanation

Here:

1. The first array provides keys.
2. The second array provides values.
3. A new associative array is created.

Important Rule of array_combine()

Both arrays must have an equal number of elements.

Example of incorrect usage:

$keys = array("name", "age");
$values = array("Ravi");
array_combine($keys, $values);

Output

Warning: array_combine(): Both parameters should have equal number of elements

Difference Between array_merge() and array_combine()

Although both functions deal with arrays, their purpose is different.

Feature	array_merge()	array_combine()
Purpose	Merges arrays	Creates new associative array
Input	Multiple arrays	Two arrays
Key Handling	Numeric keys reindexed	First array becomes keys
Value Handling	Values merged sequentially	Second array becomes values
Element Requirement	Any number of elements	Equal elements required

Example Comparing Both Functions

$array1 = array("A", "B", "C");
$array2 = array("X", "Y", "Z");
$result1 = array_merge($array1, $array2);
$result2 = array_combine($array1, $array2);
print_r($result1);
print_r($result2);

Output

array_merge()

array_combine()

Explanation

• array_merge() joins arrays sequentially.
• array_combine() maps one array to another.

Real Life Example

Suppose you have two arrays from a database:

$columns = array("id", "name", "email");
$data = array(101, "Rohit", "rohit@gmail.com");
//Using array_combine():
$user = array_combine($columns, $data);
print_r($user);

Output:

This converts raw data into a structured associative array.

When Should You Use array_merge()?

Use array_merge() when you want to:

• Join multiple arrays
• Combine list data
• Merge results from different sources

Example:

array_merge($array1, $array2);

When Should You Use array_combine()?

Use array_combine() when you want to:

• Convert two arrays into a key-value pair
• Create associative arrays
• Map database columns to values

Example:

array_combine($keys, $values);

Conclusion

The array_merge() function is used to combine multiple arrays into a single array, making it useful for merging list data or combining results from different sources.

On the other hand, array_combine() creates a new associative array by using one array as keys and another as values. This is especially useful when converting raw data into structured key-value pairs.

array_merge() vs array_combine() – Objective Questions (MCQs)