Method for generating non-repeated random numbers in PHP

The principle is very simple. First, write a function to generate one of the 36 characters 0-Z. Each time you call the getOptions () method to generate a character, they are stored as follows: array [0] = 0, array [1] = 1 ,......, Array [35] = z.

Array ( [0] => 0 [1] => 1 [2] => 2 [3] => 3 [4] => 4 [5] => 5 [6] => 6 [7] => 7 [8] => 8 [9] => 9 [10] => a [11] => b [12] => c [13] => d [14] => e [15] => f [16] => g [17] => h [18] => i [19] => j [20] => k [21] => l [22] => m [23] => n [24] => o [25] => p [26] => q [27] => r [28] => s [29] => t [30] => u [31] => v [32] => w [33] => x [34] => y [35] => z )

Then a random number is generated between 0 and 35 as the index. In fact, a random number is taken out of the above array as the first character in the variable $ result. This Random Index will be assigned to the last one of the array and will not participate in the next round of random selection.

<? Php // generate a character function getOptions () {$ options = array (); $ result = array (); for ($ I = 48; $ I <= 57; $ I ++) {array_push ($ options, chr ($ I) ;}for ($ I = 65; $ I <= 90; $ I ++) {$ j = 32; $ small = $ I + $ j; array_push ($ options, chr ($ small);} return $ options ;} /* $ e = getOptions (); for ($ j = 0; $ j <150; $ j ++) {echo $ e [$ j];} */$ len = 10; // randomly generate an array index to achieve a random number for ($ j = 0; $ j <100; $ j ++) {$ result =" "; $ Options = getOptions (); $ lastIndex = 35; while (strlen ($ result) <$ len) {// randomly retrieve an index from 0 to 35 $ index = rand (0, $ lastIndex ); // assign the random number to the variable $ chr = $ options [$ index]; // the random number is used as part of $ result. = $ chr; $ lastIndex = $ lastIndex-1; // The last index will not participate in the next random lottery $ options [$ index] = $ options [$ lastIndex];} echo $ result. "n" ;}?>