Write a for loop in php how to#
Write a for loop in php code#

I've been working on a better way of building the list here, though it would be just as easy and far more efficient to find a list online and use that. Which isn't actually very efficient, well, not when it comes to building the list of prime numbers. Public function build_primes_to( int $n )įor ( $i = end( $this->primes ) + 1 $i is_prime( $i ) ) If ( $n % $this->primes = 0 ) return false If ( in_array( $n, $this->not_prime ) ) return false įor( $i = 0 $i primes, 0, $this->prime_count( $n ) ) ) || $i = $n $i++ ) So the most efficient way I can think of at the moment is as follow: class prime You can see a bit more information on Prime Counting on wikipedia. Pi(x) is the one I keep seeing everywhere.

Write a for loop in php how to#

Just in case you forgot, here is how to write the alternative syntax.The best way to check if a number is prime is to see if it is divisible by any prime number before it. It’s exactly the same concept as discussed in Alternative if/switch syntax Just like with conditional control structures, iteration control structures can also be written with alternative syntax. The basic idea is that we generate a block on each axis of the chunk, therefore we need to loop through each axes inside each axis, requiring three nested loops.Īs a general rule of thumb, if we need to nest more than three times, we should consider a different approach to the problem and refactor our code.Alternative loop syntax The example above is not quite the same as it would be done in a real world scenario, it is also overly simplified and unoptimized specifically for the example of multiple nested loops. We can work with either just the array values or the key/value pairs. The foreach loop has two types of syntaxes. In fact, foreach loops in PHP only work on arrays and objects and will raise an error if we try to use it with another data type.

Loop is an easy way to iterate over collection sets like arrays. However, because of its syntax, the for loop has some limitations against the while loop which we discuss further below.Foreach loop The for loop is a nice, compact version of the while loop which doesn’t allow us to forget to set or increment/decrement the counter. This was done inside the while loop execution block. The third expression is where we increment or decrement the counter.This was the main expression in the while loop. The second expression is our condition ( $i The first expression sets up the counter ( $i = 1) In the while loop this counter was outside and above the loop.Let’s do a breakdown of the expressions in the for loop: The example above is the same as the while and do-while loops. We then fetch their email address and send them an email. When we want to send an email to everyone on the list, we will need to iterate through all the users in the database one by one.

Iteration helps us with repetitive tasks and when dealing with big data.Īs an example, let’s consider a database for a mailing list which contains entries for a name and email address.

Write a for loop in php code#

Many times we will need to alter this flow and allow specific sections of code to be repeated multiple times.įor this purpose, PHP offers us various types of iteration, or looping, logic which are capable of repeating sections of code. It starts at the top and flows sequentially to the bottom. And finally, we compare each loop and explain when to use which one.īy default, the flow of an application written in PHP is sequential. We also cover so called nested loops, which are loops inside other loops. We learn how PHP can help us iterate through sections of code with while, do-while, for and foreach loop statements. In this tutorial, we learn how to control the flow of our application even further. Iteration Control (loops) PHP Loops (while, do while, foreach & for) Tutorial