# Eratosthene\'s Sieve

This is a prime number generator developed by Eratosthene\'s in Ancient Greece. Enter a number below and all primes up to that number will be shown.

Maximum number:

'; if (\$n != '') { if (\$n > 9999) { echo '

## Error

Please choose a number less than 10,000.

'; exit; } \$n = abs(floor(\$n)); \$primes = array(); // setup large array of integers for (\$i = 2; \$i <= \$n; \$i++) { \$primes[] = \$i; } // loop through array to find and eliminate factors for (\$i = 0; \$i < count(\$primes); \$i++) { for (\$j = 0; \$j < count(\$primes); \$j++) { if ((\$primes[\$j] != \$primes[\$i]) && (\$primes[\$j] % \$primes[\$i] == 0)) { // remove \$j because it is composite. array_splice(\$primes, \$j, 1); } } } // display results echo '

## Results

The prime numbers between 1 and ' , \$n , ' are:

' , implode('

', \$primes) , '

'; } \$t1 = microtime(); \$ta = explode(' ', \$t0); \$tb = explode(' ', \$t1); \$sec = \$tb[1] - \$ta[1]; \$msec = \$tb[0] - \$ta[0]; \$t = round((\$sec + \$msec), 3); echo '

Results generated in ' , \$t , ' seconds

'; echo ''; ?>