PHP generate random Password method summary _php instance

Using PHP to develop applications, especially Web applications, often requires the generation of random passwords, such as user registration to generate random passwords, user reset password also need to generate a random password. Random password is a string of fixed length, here I collected several methods to generate random strings, for your reference.

Method One:

1, generate a random integer in the 33–126, such as 35,

2, convert 35 to the corresponding ASCII character, such as 35 corresponding #

3, repeat the above 1, 2 steps n times, connected to n-bit password

The algorithm mainly uses two functions, Mt_rand (int $min, int $max) function is used to generate random integers, where $min – $max the range of ASCII code, here take 33-126, you can adjust the range as necessary, such as the ASCII code table 97– 122 digits corresponding to the a–z of the English alphabet, specific reference to the ASCII code table; the Chr (int $ascii) function is used to convert the corresponding integer $ascii to the corresponding character.

function Create_password ($PW _length = 8) {$randpwd = '; for ($i = 0; $i < $PW _length; $i + +)  {  $randpwd. = Chr ( Mt_rand (33, 126)); } return $randpwd;}

Call this function, pass length parameter $pw_length = 6

Echo Create_password (6);

Method Two:

1. Preset a string $chars, including a–z,a–z,0–9, and some special characters

2. Randomly take a character in a $chars string

3, repeat the second step n times, can get the length of the password of n

function Generate_password ($length = 8) {//password character set, you can add any character you need $chars = ' Abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrst uvwxyz0123456789!@#$%^&* ()-_ []{}<>~ ' +=,.;:/?| '; $password = "; for ($i = 0; $i < $length; $i + +)  {/  /provides two ways to get  a character here///The first is to use SUBSTR to intercept any one character in $chars;  //The second is to take a character array $c Any element of the HARs  //$password. = substr ($chars, Mt_rand (0, strlen ($chars)-1), 1);  $password. = $chars [Mt_rand (0, strlen ($chars)-1)]; } return $password;}

Method Three:

1, preset a character array $chars, including a–z,a–z,0–9, and some special characters

2. Randomly select $length elements from the array $chars by Array_rand ()

3, according to the obtained key an array group $keys, from the array $chars remove the character stitching string. The disadvantage of the method is that the same characters are not repeated.

function Make_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 ', '! ',  ' @ ', ' # ', ' $ ', '% ', ' ^ ', ' & ', ' * ', ' (', ') ', '-', ' _ ', '  [', '] ', ' {', ' } ', ' < ', ' > ', ' ~ ', ' ', ' + ', ' = ', ', ', '. ', '; ', ': ', '  /', '? ', ' | '; $length number of element key names are randomly taken in the $chars $keys = Array_rand ($chars, $length);  $password = "; for ($i = 0; $i < $length; $i + +) {  //to concatenate $length array elements into string  $password. = $chars [$keys [$i]];} return $password; }

Method Four:

This method is reproduced in this article by the blue Ideal, a netizen provides a new method, the algorithm is simple, the code is short, just because the MD5 () function of the return value of the reason, the generated password only includes letters and numbers, but also a good way. Algorithm idea:

1. Time () Gets the current Unix timestamp

2, the first step to obtain the timestamp for MD5 () encryption

3, the second step to encrypt the result, intercept n-bit is the desired password

function Get_password ($length = 8) {$STR = substr (MD5 (Time ()), 0, 6); return $str;}

Time Efficiency comparison

We use the following PHP code, calculate the above 4 random password generation function generated 6-bit password run time, and then a simple comparison of their time efficiency.

<?phpfunction getmicrotime () {list ($usec, $sec) = Explode ("", Microtime ()); return (float) $usec + (float) $sec);} Record start Time $time_start = Getmicrotime ();//Place the PHP code to execute, such as://Echo Create_password (6);//record end time $time_end = Getmicrotime (); $time = $time _end-$time _start; Total elapsed time of output echo "Execution time $time seconds";? >

Method Five:

function rand_string ($len = +, $keyword = ") {if (strlen ($keyword) > $len) {//keyword cannot be longer than total length  return false;} $STR = ''; $chars = ' abcdefghijkmnpqrstuvwxyz23456789abcdefghijkmnpqrstuvwxyz '; Remove 1 with the letter L anti-aliasing    if ($len > strlen ($chars)) {//number of digits too long repeat string a certain number of times  $chars = Str_repeat ($chars, Ceil ($len/strlen ($ (chars))); } $chars = Str_shuffle ($chars); Scrambled string $str = substr ($chars, 0, $len); if (!empty ($keyword)) {  $start = $len-strlen ($keyword);  $str = Substr_replace ($str, $keyword, Mt_rand (0, $start), strlen ($keyword)); Inserts a keyword from a random position} return $str;} Echo rand_string (+, "AB"); Output example:v8bny6smkeywordb?>

The final result is:

Method One: 9.8943710327148E-5 seconds

Method Two: 9.6797943115234E-5 seconds

Method Three: 0.00017499923706055 seconds

Method Four: 3.4093856811523E-5 seconds

It can be seen that the execution time of method one and method two is similar, the method four run time is shortest, and the running time of method Three is a little longer.

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