Declare strict_types directive in PHP - Time & Space Complexity

Time Complexity: Declare strict_types directive

O(n)

Understanding Time Complexity

Let's explore how the declare(strict_types=1) directive affects PHP code execution time.

We want to see if enabling strict types changes how long the code takes as input grows.

Scenario Under Consideration

Analyze the time complexity of this PHP function with strict types declared.

declare(strict_types=1);

function sumArray(array $numbers): int {
    $total = 0;
    foreach ($numbers as $num) {
        $total += $num;
    }
    return $total;
}

This function adds all numbers in an array and returns the sum, with strict type checking enabled.

Identify Repeating Operations

Look at what repeats as input grows.

• Primary operation: Looping through each element in the array.
• How many times: Once for every item in the input array.

How Execution Grows With Input

As the array gets bigger, the function does more additions, one per item.

Input Size (n)	Approx. Operations
10	10 additions
100	100 additions
1000	1000 additions

Pattern observation: The work grows directly with the number of items.

Final Time Complexity

Time Complexity: O(n)

This means the time to run grows in a straight line with the input size.

Common Mistake

[X] Wrong: "Using declare(strict_types=1) makes the function slower as input grows."

[OK] Correct: Strict types only check types once per call, not inside the loop, so it doesn't add work that grows with input size.

Interview Connect

Understanding how language features like strict types affect performance helps you write clear and efficient code, a skill valued in real projects and interviews.

Self-Check

What if we removed the declare(strict_types=1) directive? How would the time complexity change?