PHP Program to Find Largest Number in Array

In PHP, you can find the largest number in an array using the built-in function max($array), for example: $largest = max($array);.

Examples

Input[1, 2, 3, 4, 5]

Output5

Input[-10, 0, 5, 3, 9]

Output9

Input[7]

Output7

How to Think About It

To find the largest number in an array, look at each number one by one and remember the biggest number you have seen so far. Compare each new number with the current biggest and update it if the new number is bigger.

Algorithm

1

Start with the first number as the largest.

2

Go through each number in the array one by one.

3

If a number is bigger than the current largest, update the largest to this number.

4

After checking all numbers, return the largest number found.

Code

php

<?php
$array = [3, 5, 1, 9, 2];
$largest = max($array);
echo "Largest number is: " . $largest;
?>

Output

Largest number is: 9

Dry Run

Let's trace the array [3, 5, 1, 9, 2] through the code using the max function.

1

Initial array

Array is [3, 5, 1, 9, 2]

2

Find max

max([3, 5, 1, 9, 2]) returns 9

3

Print result

Output is 'Largest number is: 9'

Iteration	Current Number	Largest So Far
1	3	3
2	5	5
3	1	5
4	9	9
5	2	9

Why This Works

Step 1: Use max function

The max() function in PHP quickly finds the largest value in an array without manual looping.

Step 2: Store result

We save the largest number found into a variable to use or display later.

Step 3: Print output

Using echo, we show the largest number to the user.

Alternative Approaches

Manual loop to find largest

php

<?php
$array = [3, 5, 1, 9, 2];
$largest = $array[0];
foreach ($array as $num) {
    if ($num > $largest) {
        $largest = $num;
    }
}
echo "Largest number is: " . $largest;
?>

This method shows how to find the largest number without built-in functions, useful for learning or custom logic.

Sort array and pick last element

php

<?php
$array = [3, 5, 1, 9, 2];
sort($array);
echo "Largest number is: " . $array[count($array) - 1];
?>

Sorting the array and taking the last element also finds the largest number but is less efficient than max() for this task.

Complexity: O(n) time, O(1) space

Time Complexity

The program checks each element once, so the time grows linearly with the number of elements, making it O(n).

Space Complexity

It uses only a few extra variables regardless of input size, so space complexity is O(1).

Which Approach is Fastest?

Using max() is fastest and simplest; manual looping is similar but more code; sorting is slower due to extra operations.

Approach	Time	Space	Best For
max() function	O(n)	O(1)	Simple and fast for any array size
Manual loop	O(n)	O(1)	Learning how to find max without built-ins
Sorting array	O(n log n)	O(1)	When array needs sorting anyway