PHP Program to Print Prime Number from 1 to N
Given a number N, the task is to print all prime numbers in a range from 1 to N in PHP.
Examples:
Input: N = 10
Output: 2, 3, 5, 7
Input: N = 50
Output: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47
Print Prime Numbers using PHP for Loop
- First, take the number N as input.
- Then use a for loop to iterate the numbers from 1 to N
- Then check for each number to be a prime number. If it is a prime number, print it.
Example:
PHP
<?php function isPrime( $n ) { if ( $n == 1 || $n == 0) { return false; } // Run a loop from 2 to sqrt(n) for ( $i = 2; $i <= sqrt( $n ); $i ++) { if ( $n % $i == 0) { return false; } } return true; } // Driver code $N = 50; // Check for every number from 1 to N for ( $i = 1; $i <= $N ; $i ++) { if (isPrime( $i )) { echo $i . " " ; } } ?> |
Output
2 3 5 7 11 13 17 19 23 29 31 37 41 43 47
Print Prime Numbers using Optimized Brute Force
This approach optimizes the brute force method by avoiding redundant checks.
Example:
PHP
<?php function isPrime( $number ) { if ( $number < 2) { return false; } if ( $number == 2 || $number == 3) { return true; } if ( $number % 2 == 0 || $number % 3 == 0) { return false; } $i = 5; $w = 2; while ( $i * $i <= $number ) { if ( $number % $i == 0) { return false; } $i += $w ; $w = 6 - $w ; } return true; } function printPrimes( $N ) { for ( $i = 2; $i <= $N ; $i ++) { if (isPrime( $i )) { echo $i . " " ; } } } // Driver code $N = 50; printPrimes( $N ); ?> |
Output
2 3 5 7 11 13 17 19 23 29 31 37 41 43 47