Several methods of generating random numbers in PHP

The first method uses Mt_rand ()

function Getrandstr ($length) {$str = ' abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789 '; $len =strlen ( $STR)-1; $randstr = ", for ($i =0; $i < $length; $i + +) {$num =mt_rand (0, $len); $randstr. = $str [$num];} return $RANDSTR;} $number =getrandstr (6); Echo $number;

　

The second method (fastest)

functionMake_password ($length= 8 ){    //password character Set, you can add any character you need    $chars=Array(' A ', ' B ', ' C ', ' d ', ' e ', ' f ', ' g ', ' h ', ' I ', ' j ', ' K ', ' l ', ' m ', ' n ', ' o ', ' P ', ' Q ', ' R ', ' s ', ' t ', ' u ', ' V ', ' W ', ' x ', ' y ', ' z ', ' A ', ' B ', ' C ', ' D ', ' E ', ' F ', ' G ', ' H ', ' I ', ' J ', ' K ', ' L ', ' M ', ' N ', ' O ', ' P ', ' Q ', ' R ', ' S ', ' T ', ' U ', ' V ', ' W ', ' X ', ' Y ', ' Z ', ' 0 ', ' 1 ', ' 2 ', ' 3 ', ' 4 ', ' 5 ', ' 6 ', ' 7 ', ' 8 ', ' 9 ', '! ', ' @ ', ' # ', ' $ ', '% ', ' ^ ', ' & ', ' * ', ' (', ' ', '-', ' _ ', ' [', '] ', ' {', '} ', ' < ', ' > ', ' ~ ', ' ', ' ' + ', ' = ', ', ', ', ', ', ', ', '/', '? ', |); //randomly take $length number of element key names in the $chars    $keys=Array_rand($chars,$length); $password= ' ';  for($i= 0;$i<$length;$i++)    {        //concatenate $length array elements into a string        $password.=$chars[$keys[$i]]; }    return $password;}

The third Kind takes the time stamp

function $length = 8 ) {    $strsubstr(Time$length) (MD5);   MD5 encryption, time () the current timestamp    return$str;}

Fourth type of scrambled string

function Getrandstr () {$str= ' ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890 '; $randStr Str_shuffle ($str); // Scrambled String $rands substr ($randStr, 0,6); // substr (string,start,length); Returns part of a string return $rands ;}

5//start to create verification code (directly with function generation, relatively convenient and quick)

$code Rand (10000, 99999);

PHP Mt_rand generate 0~1 random decimals effect comparison

Lcg_value description

float Lcg_value (void)
Lcg_value () returns a pseudo-random number with a range of (0, 1). This function combines two co-generators with a period of 2^31-85 and 2^31-249. The period of this function is equal to the product of the two primes.

Returns: the pseudo-random number of the range (0, 1).

<? PHP  for ($i$i$i+ +)    {echolcg_value().  Php_eol;}? >

Output:

0.11516515851995
0.064684551575297
0.68275174031189
0.55730746529099
0.70215008878091

Comparison of two generation 0~1 random decimal methods

1. Execution Time Comparison

Executes 100,000 times based on the Mt_rand () and Mt_getrandmax () algorithm run time

<?PHP/** * Generate 0~1 random decimals * @param int $min * @param int $max * @return Float*/functionRandfloat ($min=0,$max=1){    return $min+Mt_rand()/Mt_getrandmax() * ($max-$min);} //Get MicrotimefunctionGet_microtime () {List($usec,$sec) =Explode(‘ ‘,Microtime()); return(float)$usec+ (float)$sec;} //Record start time$starttime=get_microtime ();//execute 100,000 times to get random decimals for($i= 0;$i<100000;$i++) {randfloat ();}//Record End Time$endtime=get_microtime ();//Output Run timeprintf("Run time%f ms\r\n", ($endtime-$starttime) *1000);?>

Output: Run time 266.893148 ms

Run time of Lcg_value () 100,000 times

<?PHP//Get MicrotimefunctionGet_microtime () {List($usec,$sec) =Explode(‘ ‘,Microtime()); return(float)$usec+ (float)$sec;} //Record start time$starttime=Get_microtime (); //execute 100,000 times to get random decimals for($i= 0;$i<100000;$i++){    Lcg_value();} //Record End Time$endtime=Get_microtime (); //Output Run timeprintf("Run time%f ms\r\n", ($endtime-$starttime) *1000);?>

Output: Run time 86.178064 ms

Execution time comparison, because Lcg_value () is directly php native method, while Mt_rand () and Mt_getrandmax () need to call two methods, and need to calculate, so Lcg_value () execution time is about 3 times times faster.

2. Comparison of random effects

Random effects based on the Mt_rand () and Mt_getrandmax () algorithms

<?PHP/** * Generate 0~1 random decimals * @param int $min * @param int $max * @return Float*/functionRandfloat ($min=0,$max=1){    return $min+Mt_rand()/Mt_getrandmax() * ($max-$min);} Header(' Content-type:image/png ');$im= Imagecreatetruecolor (512, 512);$color 1= Imagecolorallocate ($im, 255, 255, 255);$color 2= Imagecolorallocate ($im, 0, 0, 0); for($y= 0;$y<512;$y++){     for($x= 0;$x<512;$x++){        $rand=randfloat (); if(round($rand, 2) >=0.5) {Imagesetpixel ($im,$x,$y,$color 1); }Else{Imagesetpixel ($im,$x,$y,$color 2); }}}imagepng ($im); Imagedestroy ($im);?>

Random effects of Lcg_value ()

<?PHPHeader(' Content-type:image/png ');$im= Imagecreatetruecolor (512, 512);$color 1= Imagecolorallocate ($im, 255, 255, 255);$color 2= Imagecolorallocate ($im, 0, 0, 0); for($y= 0;$y<512;$y++){     for($x= 0;$x<512;$x++){        $rand=Lcg_value(); if(round($rand, 2) >=0.5) {Imagesetpixel ($im,$x,$y,$color 1); }Else{Imagesetpixel ($im,$x,$y,$color 2); }}}imagepng ($im); Imagedestroy ($im);?>

Several methods of generating random numbers in PHP