Print prime numbers from 1 to N in reverse order | PHP program to print all primes between 1 to N in reverse order using Sieve of Eratosthenes ; Create a boolean array " prime [ 0 . . n ] " and initialize all entries it as true . A value in prime [ i ] will finally be false if i is Not a prime , else true . ; If prime [ p ] is not changed , then it is a prime ; Update all multiples of p ; Print all prime numbers in reverse order ; static input ; to display ; Reverseorder ( $N ) ; calling the function
< ? php function Reverseorder ( $ n ) { $ prime = array_fill ( 0 , $ n + 1 , true ) ; for ( $ p = 2 ; $ p * $ p <= $ n ; $ p ++ ) { if ( $ prime [ $ p ] == true ) { for ( $ i = $ p * 2 ; $ i <= $ n ; $ i += $ p ) $ prime [ $ i ] = false ; } } for ( $ p = $ n ; $ p >= 2 ; $ p -- ) if ( $ prime [ $ p ] ) echo $ p . " " ; } $ N = 25 ; echo " Prime ▁ number ▁ in ▁ reverse ▁ order STRNEWLINE " ; if ( $ N == 1 ) echo " No ▁ prime ▁ no ▁ exist ▁ in ▁ this ▁ range " ; else ? >