note 72391 added to function.array-product

An observation about the _use_ of array_product with primes: $a=$arrayOfSomePrimes=(2,3,11); // 2 being the first prime (these days) $codeNum=array_product($a); // gives 66 (== 2*3*11) echo "unique product(\$a) = " . array_product($a) . "\n"; The 66 can (only) be split into its original primes, which can be transformed into their place in the row of primes (2,3,5,7,11,13,17,19...) giving (1,2,3,4,5,6,7,8...) The 66 gives the places {1,2,5} in the row of primes. The number "66" is unique as a code for {1,2,5} So you can define the combination of table-columns {1,2,5} in "66". The bigger the combination, the more efficient in memory/transmission, the less in calculation. ---- Server IP: 194.109.193.94 Probable Submitter: 81.68.120.158 ---- Manual Page -- http://www.php.net/manual/en/function.array-product.php Edit -- https://master.php.net/note/edit/72391 Del: integrated -- https://master.php.net/note/delete/72391/integrated Del: useless -- https://master.php.net/note/delete/72391/useless Del: bad code -- https://master.php.net/note/delete/72391/bad+code Del: spam -- https://master.php.net/note/delete/72391/spam Del: non-english -- https://master.php.net/note/delete/72391/non-english Del: in docs -- https://master.php.net/note/delete/72391/in+docs Del: other reasons-- https://master.php.net/note/delete/72391 Reject -- https://master.php.net/note/reject/72391 Search -- https://master.php.net/manage/user-notes.php