PHP Question: Scope Resolution

6th April 2011 - 2 minutes read time

Question

What is printed after the following code has been run?

function calc() {
    $a = 1000;
    return $a;
}

$a = 1;
calc();
print $a;

 









 

Answer

The answer here is "1", and is an example of what is called 'scope resolution'. Essentially, anything that happens inside the calc() function will stay inside the function, so any variables that are created are thrown away after the function has completed its task. Therefore, variable $a that is defined outside the function is a completely different variable to the $a defined inside the function and so setting the value inside the function will do nothing to the variable outside.

It is possible to change the value of a variable from inside a function, but that is only if the variable has been passed by reference, which the example above doesn't do.

PHP

Comments

I like the idea of this series, but what if you provided the answer 24h after you posted the question? I mean, let's see what the readers think about it? It might bring pretty interesting answers.

Submitted by Mihai Baboi on Thu, 04/07/2011 - 06:24

Permalink

Nice suggestion Mihai I might do that with the next question and see what happens. Would you belive that I once asked this question to a room of developers who used PHP every day and only 30% got it right?

Philip Norton

Submitted by philipnorton42 on Thu, 04/07/2011 - 13:18

Permalink

Add new comment

The content of this field is kept private and will not be shown publicly.

Related Content

A Look At Benford's Law

11th May 2025

Benford's Law is an interesting heuristic in data analysis. It states that in any large collection of numbers that are created naturally, you should expect to see numbers starting with the number 1 about 30% of the time. The frequency distribution of numbers states that 2 should appear about 17% of the time, down to 9 being seen just 5% of the time.

Read more

Protecting A Page From Being Directly Accessed With PHP

27th April 2025

I was thinking recently about the number of ways in which I could restrict access to a page using PHP.

The obvious option is to create a user authentication system, but in some situations that is overkill for what is required. If you just want to prevent users from going directly to a certain page then there are a few options open to you.

Read more

Generating Colour Palettes From Images In PHP

4th August 2024

A common web design pattern is to incorporate an image into the design of the page. This creates a tighter integration with the image and the rest of the page.

The main issue in designing a page around the image is that the colours of the page must match the image. Otherwise this creates a dissonance between the image and the styles of the site.

Read more

Validating XML Files With XML Schema Definitions In PHP

21st July 2024

XML is a useful format for configuration, data storage, and transmitting data from one system to another. As a human readable format that can be easily read by machines it quickly gained favor in lots of different systems as a mechanism for data storage.

Read more

Approximating Pi Using A Circle And A Square

26th May 2024

Pi day was a few weeks ago, but I came across this simple approximation of pi recently and decided to put together an example in PHP since it seemed pretty simple.

This approximation of pi centers around a real world example, but we can simulate this using some code.

Read more