An example of a random number of randomly generated letters in PHP

In many system environments everyone uses a combination of letters to encode. below for you to introduce the use of PHP randomly generated random number of combinations of letters, interested friends can understand the next

In many systems environment everyone will use the letter combination of various coding, the following recommendations are very useful PHP code.     $num are grouped by several letters.  The code is as follows: function Makecode ($num =4) {$re = ";  $s = ' abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz ';  while (strlen ($re) < $num) {$re. = $s [rand (0, strlen ($s)-1)];//randomly generate a character from the $s} return $re; }