{"id":1,"date":"2019-08-28T19:04:10","date_gmt":"2019-08-28T19:04:10","guid":{"rendered":"https:\/\/tutorialio.com\/?p=1"},"modified":"2019-08-28T19:04:10","modified_gmt":"2019-08-28T19:04:10","slug":"random-number-functions-in-php","status":"publish","type":"post","link":"https:\/\/hellonitish.com\/blog\/random-number-functions-in-php\/","title":{"rendered":"Random Number Functions in PHP"},"content":{"rendered":"\n\n\n\n\n\n\n\n\n
Random Number Functions Functions in PHP<\/caption>\n<\/caption>\n
Function Name<\/th>\nFunction Description<\/th>\n<\/tr>\n
getrandmax()<\/a><\/td>\nShow largest possible random value<\/td>\n<\/tr>\n
mt_getrandmax()<\/a><\/td>\nShow largest possible random value<\/td>\n<\/tr>\n
mt_rand()<\/a><\/td>\nGenerate a random value via the Mersenne Twister Random Number Generator<\/td>\n<\/tr>\n
mt_srand()<\/a><\/td>\nSeeds the Mersenne Twister Random Number Generator<\/td>\n<\/tr>\n
rand()<\/a><\/td>\nGenerate a random integer<\/td>\n<\/tr>\n
srand()<\/a><\/td>\nSeed the random number generator<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

PHP getrandmax()<\/code> Function<\/h2>\n

PHP getrandmax()<\/code> Usage<\/h3>\n

The PHP getrandmax()<\/code><\/code> function will give you the maximum value that can be returned by a call to rand()<\/code>.<\/p>\n

PHP getrandmax()<\/code> Syntax<\/h3>\n
 getrandmax ( void ) : int<\/code><\/pre>\n
PHP getrandmax()<\/code> Parameters<\/h3>\n
    <\/ol>\n
    This function does not accept any parameters.<\/p>\n
    PHP getrandmax()<\/code> Return Value<\/h3>\n
    The PHP getrandmax()<\/code> function returns d by rand()<\/code><\/p>\n
    PHP mt_getrandmax()<\/code> Function<\/h2>\n
    PHP mt_getrandmax()<\/code> Usage<\/h3>\n
    The PHP mt_getrandmax()<\/code><\/code> function will give you the maximum value that can be returned by a call to mt_rand()<\/code>.<\/p>\n
    PHP mt_getrandmax()<\/code> Syntax<\/h3>\n
     mt_getrandmax ( void ) : int<\/code><\/pre>\n
    PHP mt_getrandmax()<\/code> Parameters<\/h3>\n
      <\/ol>\n
      This function does not accept any parameters.<\/p>\n
      PHP mt_getrandmax()<\/code> Return Value<\/h3>\n
      The PHP mt_getrandmax()<\/code> function returns the maximum random value returned by a call to mt_rand()<\/code> without arguments, which is the maximum value that can be used for its max<\/code> parameter without the result being scaled up (and therefore less random).<\/p>\n
      PHP mt_getrandmax()<\/code> Working Examples<\/h3>\n
      1. Calculate a random floating-point number<\/h4>\n
      <?php\nfunction randomFloat($min = 0, $max = 1) {\n    return $min + mt_rand() \/ mt_getrandmax() * ($max - $min);\n}\nvar_dump(randomFloat());\nvar_dump(randomFloat(2, 20));\n?><\/code><\/pre>\n
      Output of the above code:<\/p>\n
      float(0.91601131712832)\nfloat(16.511210331931)<\/code><\/pre>\n
      PHP mt_rand()<\/code> Function<\/h2>\n
      PHP mt_rand()<\/code> Usage<\/h3>\n
      The PHP mt_rand()<\/code><\/code> function will generate a random value via the Mersenne Twister Random Number Generator.<\/p>\n
      PHP mt_rand()<\/code> Syntax<\/h3>\n
       mt_rand ( void ) : int<\/code><\/pre>\n
       mt_rand ( int $min , int $max ) : int<\/code><\/pre>\n
      PHP mt_rand()<\/code> Parameters<\/h3>\n
        \n
      1. \n
        min<\/code> \u2014 Optional lowest value to be returned (default: 0) <\/p>\n<\/li>\n
      2. \n
        max<\/code> \u2014 Optional highest value to be returned (default: mt_getrandmax()<\/code>) <\/p>\n<\/li>\n<\/ol>\n
        PHP mt_rand()<\/code> Return Value<\/h3>\n
        The PHP mt_rand()<\/code> function returns a random integer value between min<\/code> (or 0) and max<\/code> (or mt_getrandmax()<\/code>, inclusive), or FALSE<\/code> if max<\/code> is less than min<\/code>.<\/p>\n
        PHP mt_rand()<\/code> Working Examples<\/h3>\n
        1. mt_rand() example<\/h4>\n
        <?php\necho mt_rand() . \"\\n\";\necho mt_rand() . \"\\n\";\necho mt_rand(5, 15);\n?><\/code><\/pre>\n
        Output of the above code:<\/p>\n
        1604716014\n1478613278\n6<\/code><\/pre>\n
        Changelog for PHP mt_rand()<\/code> Function<\/h3>\n
        7.2.0 \u2014 <\/strong> mt_rand()<\/code> has received a bug fix for a modulo bias bug. This means that sequences generated with a specific seed may differ from PHP 7.1 on 64-bit machines. <\/p>\n
        7.1.0 \u2014 <\/strong> rand()<\/code> has been made an alias of mt_rand()<\/code>. <\/p>\n
        7.1.0 \u2014 <\/strong> mt_rand()<\/code> has been updated to use the fixed, correct, version of the Mersenne Twister algorithm. To fall back to the old behaviour, use mt_srand()<\/code> with MT_RAND_PHP<\/code> as the second parameter. <\/p>\n
        5.3.4 \u2014 <\/strong> Issues an E_WARNING<\/code> and returns FALSE<\/code> if max<\/code> < min<\/code>. <\/p>\n
        Important Points about PHP mt_rand()<\/code> Function<\/h3>\n
          \n
        1. \n
          This function does not generate cryptographically secure values, and should not be used for cryptographic purposes. If you need a cryptographically secure value, consider using random_int()<\/code>, random_bytes()<\/code>, or openssl_random_pseudo_bytes()<\/code> instead.<\/p>\n<\/li>\n
        2. \n
           min<\/code> max<\/code> range must be within the range mt_getrandmax()<\/code>. i.e. (max<\/code> – min<\/code>) <= mt_getrandmax()<\/code> Otherwise, mt_rand()<\/code> may return poorer random numbers than it should. <\/p>\n<\/li>\n<\/ol>\n
          Additional Tips from Fellow Developers<\/h3>\n
          Contributed By: cyrax21<\/p>\n
          i wanted to spot out the big difference between rand and mt_rand when producing images using randomness as noise. \n \nfor example this is a comparation between rand and mt_rand on a 400x400 pixel png: http:\/\/oi43.tinypic.com\/vwtppl.jpg \n \ncode: \n
          <?php \nheader(\"Content-type: image\/png\"); \n$sizex=800; \n$sizey=400; \n \n$img = imagecreatetruecolor($sizex,$sizey); \n$ink = imagecolorallocate($img,255,255,255); \n \nfor($i=0;$i<$sizex\/2;$i++) { \n  for($j=0;$j<$sizey;$j++) { \n  imagesetpixel($img, rand(1,$sizex\/2), rand(1,$sizey), $ink); \n  } \n} \n \nfor($i=$sizex\/2;$i<$sizex;$i++) { \n  for($j=0;$j<$sizey;$j++) { \n  imagesetpixel($img, mt_rand($sizex\/2,$sizex), mt_rand(1,$sizey), $ink); \n  } \n} \n \nimagepng($img); \nimagedestroy($img); \n?>
           \n \nthe differences reduce when reducing the pixels of the image.. infact for a 100x100 pixel image the noise produced from the rand function is much more realistic than how it is for a 400x400 image: http:\/\/oi39.tinypic.com\/5k0row.jpg \n \n(rand is on the left, mt_rand on the right)<\/pre>\n
          <\/code><\/p>\n
          PHP mt_srand()<\/code> Function<\/h2>\n
          PHP mt_srand()<\/code> Usage<\/h3>\n
          The PHP mt_srand()<\/code><\/code> function will seeds the Mersenne Twister Random Number Generator.<\/p>\n
          PHP mt_srand()<\/code> Syntax<\/h3>\n
           mt_srand ([ int $seed [, int $mode = MT_RAND_MT19937 ]] ) : void<\/code><\/pre>\n
          PHP mt_srand()<\/code> Parameters<\/h3>\n
            \n
          1. \n
            seed<\/code> \u2014 An arbitrary integer seed value. <\/p>\n<\/li>\n
          2. \n
            mode<\/code> \u2014 Use one of the following constants to specify the implementation of the algorithm to use. <\/p>\n<\/li>\n<\/ol>\n
            PHP mt_srand()<\/code> Return Value<\/h3>\n
            The PHP mt_srand()<\/code> function returns d.<\/p>\n
            PHP mt_srand()<\/code> Working Examples<\/h3>\n
            1. mt_srand() example<\/h4>\n
            <?php\n\/\/ seed with microseconds\nfunction make_seed()\n{\n  list($usec, $sec) = explode(' ', microtime());\n  return $sec + $usec * 1000000;\n}\nmt_srand(make_seed());\n$randval = mt_rand();\n?><\/code><\/pre>\n
            Changelog for PHP mt_srand()<\/code> Function<\/h3>\n
            7.1.0 \u2014 <\/strong> srand()<\/code> has been made an alias of mt_srand()<\/code>. <\/p>\n
            7.1.0 \u2014 <\/strong> mt_rand()<\/code> has been updated to use the fixed, correct, version of the Mersenne Twister algorithm. To fall back to the old behaviour, use mt_srand()<\/code> with MT_RAND_PHP<\/code> as the second parameter. <\/p>\n
            5.2.1 \u2014 <\/strong> The Mersenne Twister implementation in PHP now uses a new seeding algorithm by Richard Wagner. Identical seeds no longer produce the same sequence of values they did in previous versions. This behavior is not expected to change again, but it is considered unsafe to rely upon it nonetheless. <\/p>\n
            PHP rand()<\/code> Function<\/h2>\n
            PHP rand()<\/code> Usage<\/h3>\n
            The PHP rand()<\/code><\/code> function will give you a pseudo-random integer between 0 and getrandmax()<\/code>. If you want a random number between 5 and 15 (inclusive), for example, use rand(5, 15)<\/strong>.<\/p>\n
            PHP rand()<\/code> Syntax<\/h3>\n
             rand ( void ) : int<\/code><\/pre>\n
             rand ( int $min , int $max ) : int<\/code><\/pre>\n
            PHP rand()<\/code> Parameters<\/h3>\n
              \n
            1. \n
              min<\/code> \u2014 The lowest value to return (default: 0) <\/p>\n<\/li>\n
            2. \n
              max<\/code> \u2014 The highest value to return (default: getrandmax()<\/code>) <\/p>\n<\/li>\n<\/ol>\n
              PHP rand()<\/code> Return Value<\/h3>\n
              The PHP rand()<\/code> function returns a pseudo random value between min<\/code> (or 0) and max<\/code> (or getrandmax()<\/code>, inclusive).<\/p>\n
              PHP rand()<\/code> Working Examples<\/h3>\n
              1. rand() example<\/h4>\n
              <?php\necho rand() . \"\\n\";\necho rand() . \"\\n\";\necho rand(5, 15);\n?><\/code><\/pre>\n
              Output of the above code:<\/p>\n
              7771\n22264\n11<\/code><\/pre>\n
              Changelog for PHP rand()<\/code> Function<\/h3>\n
              7.2.0 \u2014 <\/strong> rand()<\/code> has received a bug fix for a modulo bias bug. This means that sequences generated with a specific seed may differ from PHP 7.1 on 64-bit machines. <\/p>\n
              7.1.0 \u2014 <\/strong> rand()<\/code> has been made an alias of mt_rand()<\/code>. <\/p>\n
              Important Points about PHP rand()<\/code> Function<\/h3>\n
                \n
              1. \n
                This function does not generate cryptographically secure values, and should not be used for cryptographic purposes. If you need a cryptographically secure value, consider using random_int()<\/code>, random_bytes()<\/code>, or openssl_random_pseudo_bytes()<\/code> instead.<\/p>\n<\/li>\n
              2. \n
                 min<\/code> max<\/code> range must be within the range getrandmax()<\/code>. i.e. (max<\/code> - min<\/code>) <= getrandmax()<\/code> Otherwise, rand()<\/code> may return poor-quality random numbers. <\/p>\n<\/li>\n<\/ol>\n
                Additional Tips from Fellow Developers<\/h3>\n
                Contributed By: Anonymous<\/p>\n
                quick way to generate randomish numbers and simple strings.\nno messing around with functions, so you can just pop the line into the middle of your existing code.\nnot the most perfect for sure, but ok for plenty of situations...\n
                <?php\n$random_number = intval( \"0\" . rand(1,9) . rand(0,9) . rand(0,9) . rand(0,9) . rand(0,9) ); \/\/ random(ish) 5 digit int\n$random_string = chr(rand(65,90)) . chr(rand(65,90)) . chr(rand(65,90)) . chr(rand(65,90)) . chr(rand(65,90)); \/\/ random(ish) 5 character string\n?>
                \nhope someone finds it useful for somthing.\nregards,\ndeeeeeen alxndr0u<\/pre>\n
                <\/code><\/p>\n
                Contributed By: phpdev<\/p>\n
                Here's an interesting note about the inferiority of the rand() function. Try, for example, the following code...\n
                <?php\n$r = array(0,0,0,0,0,0,0,0,0,0,0);\nfor ($i=0;$i<1000000;$i++) {\n  $n = rand(0,100000);\n  if ($n<=10) {\n    $r[$n]++;\n  }\n}\nprint_r($r); \n?>
                \nwhich produces something similar to the following output (on my windows box, where RAND_MAX is 32768):\nArray\n(\n    [0] => 31\n    [1] => 0\n    [2] => 0\n    [3] => 31\n    [4] => 0\n    [5] => 0\n    [6] => 30\n    [7] => 0\n    [8] => 0\n    [9] => 31\n    [10] => 0\n)\nWithin this range only multiples of 3 are being selected. Also note that values that are filled are always 30 or 31 (no other values! really!) \nNow replace rand() with mt_rand() and see the difference...\nArray\n(\n    [0] => 8\n    [1] => 8\n    [2] => 14\n    [3] => 16\n    [4] => 9\n    [5] => 11\n    [6] => 8\n    [7] => 9\n    [8] => 7\n    [9] => 7\n    [10] => 9\n)\nMuch more randomly distributed!\nConclusion: mt_rand() is not just faster, it is a far superior algorithm.<\/pre>\n
                <\/code><\/p>\n
                PHP srand()<\/code> Function<\/h2>\n
                PHP srand()<\/code> Usage<\/h3>\n
                The PHP srand()<\/code><\/code> function will seeds the random number generator with seed<\/code> or with a random value if no seed<\/code> is given.<\/p>\n
                PHP srand()<\/code> Syntax<\/h3>\n
                 srand ([ int $seed ] ) : void<\/code><\/pre>\n
                PHP srand()<\/code> Parameters<\/h3>\n
                  \n
                1. \n
                  seed<\/code> \u2014 An arbitrary integer seed value. <\/p>\n<\/li>\n<\/ol>\n
                  PHP srand()<\/code> Return Value<\/h3>\n
                  The PHP srand()<\/code> function returns d.<\/p>\n
                  PHP srand()<\/code> Working Examples<\/h3>\n
                  1. srand() example<\/h4>\n
                  <?php\n\/\/ seed with microseconds\nfunction make_seed()\n{\n  list($usec, $sec) = explode(' ', microtime());\n  return $sec + $usec * 1000000;\n}\nsrand(make_seed());\n$randval = rand();\n?><\/code><\/pre>\n
                  Changelog for PHP srand()<\/code> Function<\/h3>\n
                  7.1.0 \u2014 <\/strong> srand()<\/code> has been made an alias of mt_srand()<\/code>. <\/p>\n","protected":false},"excerpt":{"rendered":"
                  Random Number Functions Functions in PHP Function Name Function Description getrandmax() Show largest possible random value mt_getrandmax() Show largest possible random value mt_rand() Generate a random value via the Mersenne Twister Random Number Generator mt_srand() Seeds the Mersenne Twister Random Number Generator rand() Generate a random integer srand() Seed the random number generator PHP getrandmax() […]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[5,6],"class_list":["post-1","post","type-post","status-publish","format-standard","hentry","category-reference","tag-php","tag-random"],"_links":{"self":[{"href":"https:\/\/hellonitish.com\/blog\/wp-json\/wp\/v2\/posts\/1","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/hellonitish.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/hellonitish.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/hellonitish.com\/blog\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/hellonitish.com\/blog\/wp-json\/wp\/v2\/comments?post=1"}],"version-history":[{"count":0,"href":"https:\/\/hellonitish.com\/blog\/wp-json\/wp\/v2\/posts\/1\/revisions"}],"wp:attachment":[{"href":"https:\/\/hellonitish.com\/blog\/wp-json\/wp\/v2\/media?parent=1"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/hellonitish.com\/blog\/wp-json\/wp\/v2\/categories?post=1"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/hellonitish.com\/blog\/wp-json\/wp\/v2\/tags?post=1"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}