4 methods for generating random passwords in PHP

Source: Internet
Author: User
When using PHP to develop applications, especially website programs, you often need to generate random passwords. for example, if you register a user to generate a random password, you also need to generate a random password to reset the password. The random password is a string of fixed length. here I have collected several methods to generate random strings for your reference. Method 1 SyntaxHighlighter. all (); using PHP to develop applications, especially website programs, you often need to generate random passwords. for example, if you register to generate random passwords, you also need to generate a random password to reset the password.

The random password is a string of fixed length. here I have collected several methods to generate random strings for your reference.
Method 1:
1. in 33? Generate a random integer in 126, for example, 35,
2. convert 35 to corresponding ASCII characters, for example, 35 #
3. Repeat steps 1 and 2 n and connect them to a n-bit password.

This algorithm mainly uses two functions. the mt_rand (int $ min, int $ max) function is used to generate random integers, where $ min? $ Max is the range of ASCII codes. here, the value ranges from 33 to 126. you can adjust the range as needed, for example, 97 in the ASCII code table? 122 bits correspond to? The English letter of z. for details, refer 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 to pass the length parameter $ pw_length = 6
Echo create_password (6 );
?>

Method 2:
1. preset a string $ chars, including? Z,? Z, 0? 9, and some special characters
2. random character in $ chars string
3. Repeat step 2 n times to obtain a password with a length of n.
Function generate_password ($ length = 8 ){
// Password character set, which can be any character you need
$ Chars = abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789! @ # $ % ^ & * ()-_ [] {}<> ~ '= ,.;:/? |;
$ Password =;
For ($ I = 0; $ I <$ length; $ I)
{
// Two character acquisition methods are provided here
// Use substr to intercept any character in $ chars;
// The second method is to take any element of the character array $ chars.
// $ Password. = substr ($ chars, mt_rand (0, strlen ($ chars)-1), 1 );
$ Password. = $ chars [mt_rand (0, strlen ($ chars)-1)];
}
Return $ password;
}
?>

Method 3:
1. preset a character array $ chars, including? Z,? Z, 0? 9, and some special characters
2. use array_rand () to randomly select $ length elements from the array $ chars.
3. extract the string from the array $ chars based on the obtained key name array $ keys. The disadvantage of this method is that the same characters are not repeated.
Copy the code as follows:
Function make_password ($ length = 8)
{
// Password character set, which can be 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 ,!,
@, #, $, %, ^ ,&,*,(,),-,_,
[,], {,}, <,> ,~, ', = ,,,
.,;,:,/,?, | );
// Random $ length array element key names in $ chars
$ Keys = array_rand ($ chars, $ length );
$ Password =;
For ($ I = 0; $ I <$ length; $ I)
{
// Concatenate $ length array elements into strings
$ Password. = $ chars [$ keys [$ I];
}
Return $ password;
}
?>

Method 4:
This method is a new method provided by a netizen after being reproduced by the blue ideal in this article. the algorithm is simple and the code is short, just because of the return value of the md5 () function, the generated password only contains letters and numbers, but it is also a good method. Algorithm idea:
1. time () gets the current Unix timestamp
2. encrypt the timestamp obtained in step 1 with md5 ()
3. extract the data encrypted in step 2 to obtain 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 to calculate the running time of the above four random password generation functions to generate six passwords, and then compare their time efficiency.
Function getmicrotime ()
{
List ($ usec, $ sec) = explode ("", microtime ());
Return (float) $ usec (float) $ sec );
}
// Record start time
$ Time_start = getmicrotime ();
// Put the PHP code to be executed here, for example:
// Echo create_password (6 );
// Record end time
$ Time_end = getmicrotime ();
$ Time = $ time_end-$ time_start;
// Output the total running time
Echo "execution time $ time seconds ";
?>

The final result is:
Method 1: 9.8943710327148E-5 seconds
Method 2: 9.6797943115234E-5 seconds
Method 3: 0.00017499923706055 seconds
Method 4: 3.4093856811523E-5 seconds

We can see that method 1 and method 2 have almost the same execution time, and method 4 has the shortest time, while Method 3 has a longer running time.
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