How to Replace an Element Inside Array in PHP ?

Given an array containing some elements, the task is to replace an element inside the array in PHP. There are various methods to manipulate arrays, including replacing elements.

Examples:

Input: arr = [10, 20, 30, 40, 50], index_1 = 100
Output: [10, 100, 30, 40, 50]
Input: arr = ['GFG', 'Geeks', 'Hello'], index_2 = 'Welcome'
Output: ['GFG', 'Geeks', 'Welcome']

Here are some common approaches:

Approach 1: Using Index Assignment

The most straightforward way to replace an element in a PHP array is to directly assign a new value to the desired index.

<?php 

$arr = array(10, 30, 40, 50, 70); 

$arr[1] = 100; 

// Display the updated array 
print_r($arr); 

?>

Array
(
    [0] => 10
    [1] => 100
    [2] => 40
    [3] => 50
    [4] => 70
)

Approach 2: Using array_replace() Function

PHP provides the array_replace() function that merges the values of two or more arrays. It is particularly useful for replacing specific elements.

<?php 

$arr = array(10, 30, 40, 50, 70); 

$modifiedArr = array_replace($arr, [1 => 100]); 

// Display the modified array 
print_r($modifiedArr); 

?>

Array
(
    [0] => 10
    [1] => 100
    [2] => 40
    [3] => 50
    [4] => 70
)

Approach 3: Using array_splice() Function

The array_splice() function allows us to remove a portion of the array and replace it with new elements.

<?php 

$arr = array(10, 30, 40, 50, 70); 

array_splice($arr, 1, 1, 100); 

// Display the modified array 
print_r($arr); 

?>

Array
(
    [0] => 10
    [1] => 100
    [2] => 40
    [3] => 50
    [4] => 70
)

Approach 4: Using foreach Loop with Condition

In PHP, a foreach loop with a condition iterates through an array. Inside the loop, a condition (`if` statement) checks each element (`$value`) against a specified condition (`$value === 3`), allowing for targeted updates or operations based on element values.

Example: In this example we iterates through an array, replaces the first occurrence of the value 3 with 6, then stops further iteration.

<?php
$array = [1, 2, 3, 4, 5];

foreach ($array as $key => $value) {
    if ($value === 3) {
        $array[$key] = 6;
        break; // Stop iterating once the condition is met
    }
}

print_r($array); // Output: [1, 2, 6, 4, 5]
?>

Array
(
    [0] => 1
    [1] => 2
    [2] => 6
    [3] => 4
    [4] => 5
)

Approach 5: Using array_map() Function

The array_map() function applies a callback to the elements of the given arrays. It can be used to replace specific elements in an array by applying a custom function.

Example:

<?php 

$arr = array(10, 30, 40, 50, 70); 
$indexToReplace = 1; 
$newValue = 100; 

$modifiedArr = array_map(function($value, $key) use ($indexToReplace, $newValue) {
    return ($key === $indexToReplace) ? $newValue : $value;
}, $arr, array_keys($arr));

// Display the modified array 
print_r($modifiedArr); 

?>

Array
(
    [0] => 10
    [1] => 100
    [2] => 40
    [3] => 50
    [4] => 70
)

Approach 5: Using array_search() and direct assignment

This approach uses array_search() to find the index of the element to replace and then directly assigns the new value to that index.

Example:

<?php
// Example array
$arr = [10, 20, 30, 40, 50];

// Find the index of the element to replace
$index = array_search(30, $arr);

if ($index !== false) {
    // Replace the element at the found index
    $arr[$index] = 100;
}

print_r($arr); // Output: [10, 20, 100, 40, 50]
?>

Array
(
    [0] => 10
    [1] => 20
    [2] => 100
    [3] => 40
    [4] => 50
)