Using loops is one of the most basic concepts taught to a novice programmer. We always come up with a loop solution for any trivial task because we are accustomed to them. However, a more experienced programmer might write a solution without actually looping through the array using an inbuilt defined function. The PHP array_map function is an inbuilt PHP function that sends the array elements to a user-defined function. In this article, I will discuss the PHP array_map Function to modify the array in PHP.
What Is array_map Function?
array_map — Applies the callback to the elements of the given arrays
http://php.net
The PHP array_map function is an inbuilt PHP function that sends the array elements to a user-defined function. It helps to modify the contents of an array using the user-defined function and returns the modified array as output.
Syntax
array_map(callbackFunction,arr1,arr2…)
Parameters
The array_map function takes in two mandatory parameters; callbackFunction and an array. The rest of the parameters are optional.
- callbackFunction: The callback Function is a mandatory user-defined function passed to the array_map function according to which the array elements will be modified.
- $arr1: The array arr1 is a mandatory array which will be modified by the callback function.
- $arr2..$arrn: You can pass more than one array to the PHP array_map Function.
Examples
Let’s consider the following examples to understand more.
Example 1: Basic Usage with Integers
If you need to calculate the squares of all the numbers given in an array, this is what you might possibly code using a
<?php
$testNum = array(1,2,3,4,5);
foreach($testNum as $key => $num) {
$testNum[$key] = $num*$num;
}
print_r($testNum);
/* Output:
Array
(
[0] => 1
[1] => 4
[2] => 9
[3] => 16
[4] => 25
)
*/
?>
The array_map function can be used to implement the same solution as follows:
<?php
function calculateSquares($num) {
return $num*$num;
}
$testNum = array(1,2,3,4,5);
$testNum = array_map('calculateSquares', $testNum);
print_r($testNum);
/* Output:
Array
(
[0] => 1
[1] => 4
[2] => 9
[3] => 16
[4] => 25
)
*/
?>
Using Anonymous Functions with array_map
We can also use Lambda Functions (or anonymous functions) in array_map to implement the same logic as shown below:
<?php
$lambdaFunc = function($num) {
return $num * $num;
};
$testNum = array(1,2,3,4,5);
$testNum = array_map($lambdaFunc, $testNum);
print_r($testNum);
/*
Array
(
[0] => 1
[1] => 4
[2] => 9
[3] => 16
[4] => 25
)
*/
?>
Example 2: Calling a Class Method
If the method you are calling is a class method, then you can use the array_map function by passing the object reference with the method name as shown in the following example:
<?php
class TestArrayMap {
private function calculateSquares($num) {
return $num * $num;
}
public function getSquares($testNumArray) {
//Object reference passed along with method name
return array_map(array($this, 'calculateSquares'), $testNumArray);
}
}
$testArrayMapObj = new TestArrayMap();
print_r($testArrayMapObj->getSquares(array(1,2,3,4,5)));
?>
Example 3: Pre Defined PHP Functions
You may also pass PHP predefined functions as the callback method instead of creating user-defined functions. Here, we are calling the inbuilt PHP
<?php
$stringArray = array('bringing', 'knowledge', 'together');
$upperCaseArray = array_map('strtoupper', $stringArray);
print_r($upperCaseArray);
/*
Array
(
[0] => BRINGING
[1] => KNOWLEDGE
[2] => TOGETHER
)
*/
?>
Example 4: Null Callback
On passing null as the callback function, array_map merges two arrays in the following way:
<?php
$userNames = array('Vishesh', 'Sam', 'Joe');
$userEmails = array('[email protected]', '[email protected]', '[email protected]');
print_r(array_map(null, $userNames, $userEmails));
/*
Array
(
[0] => Array
(
[0] => Vishesh
[1] => [email protected]
)
[1] => Array
(
[0] => Sam
[1] => [email protected]
)
[2] => Array
(
[0] => Joe
[1] => [email protected]
)
)
*/
?>
Performance Analysis
You might be wondering
I performed the analysis by calculating the time required to calculate squares of all numbers from 1 to 1000000 using both array_map and a
<?php
/* ############## Array Map ################### */
function calculateSquares($num) {
return $num*$num;
}
$startTime = microtime(true);
$testNum = range(1,1000000);
$newArr = array_map('calculateSquares', $testNum);
$endTime = microtime(true);
echo 'Time Taken By array_map: '.($endTime - $startTime);
/* ############## For Loop #################### */
$startTimeLoop = microtime(true);
$testNum = range(1,1000000);
$newArr = array();
foreach($testNum as $key => $value) {
$newArr[] = $value * $value;
}
$endTimeLoop = microtime(true);
echo '<br/>Time Taken by Loop: '.($endTimeLoop - $startTimeLoop);
?>
As shown in the above test results the PHP array_map Function almost performs equally good as a regular foreach loop for performing the same task. However, using array_map looks better in the source code. It reduces the number of for-loops you have to write and performs the same task.
Conclusion
In this article, we discussed the use of PHP array_map function for modifying elements in an array. I also did a performance analysis for checking the time taken by a traditional for loop and using the array_map function.
You can also read more about array_map function on the official PHP documentation. Please read more articles on PHP on Concatly. Kindly leave your valuable comments below to help me improve this resource.
Vishesh is currently working as an Intermediate Software Engineer with Orion Health, New Zealand. He graduated with a Masters in Information Technology from the University of Auckland in 2021. With more than 4 years of work experience, his expertise includes Java, Python, Machine Learning, PHP, Databases, Design and Architecture.