PHP can also do big things with random functions, PHP can do big things with random functions_PHP Tutorial

PHP can also do big things. Random functions, big things in PHP. Random functions

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PHP can also do great things. This is the classic usage of PHP syntax features and related function libraries that I have summarized. It may not really be able to achieve the effect of making a big difference, but mastering these methods can be of some help in your work and study. , I hope everyone can brainstorm and make "PHP Can Do Great Things" more exciting! Please indicate the source when reprinting (3mc2.com)

2. Foreword

PHP is a common scripting language, mainly because it is easy to learn and quick to use. Almost 50% of web programs include PHP (incomplete statistics). PHP provides a wealth of functions and API interfaces for development, which allows us to use its powerful built-in functions and extensions very conveniently. This article is the second article in the series "PHP Can Do Big Things", which mainly summarizes the use of PHP in random number generation. knowledge of equipment.

3. PHP random function

PHP random functions mainly include rand, mt_rand, array_rand, as well as the randomly "arranged" (shuffled) functions shuffle and str_shuffle, which can generate uniqid with a unique ID.

1. rand generates random numbers:

<&#63;php
$base = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789';
$count = strlen($base);
$random = '';
for ($i=0; $i < 16; $i++) { 
 $random.=$base[rand(0,$count-1)];
}
echo $random;
&#63;>

The rand() function uses libc's random number generator to generate random numbers. It is generally slow and has uncertain factors. It is recommended to use the mt_rand function instead.

The getrandmax() function can return the largest random number that the rand function can generate (my system is 32767), so when setting the second parameter of the rand function, do not exceed the return value of getrandmax.

2. mt_rand generates random numbers:

<&#63;php
$base = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789';
$count = strlen($base);
$random = '';
for ($i=0; $i < 16; $i++) { 
 $random.=$base[mt_rand(0,$count-1)];
}
echo $random;
&#63;>

Many old libc random number generators have some uncertain and unknown characteristics and are slow. PHP's rand() function uses the libc random number generator by default. The mt_rand() function is informally used to replace it. This function uses the known features of » Mersenne Twister as a random number generator, which can generate random values ​​on average four times faster than rand() provided by libc. It is strongly recommended to use the mt_rand function instead of rand during development.

If the optional parameters min and max are not provided, mt_rand() returns a pseudo-random number between 0 and mt_getrandmax(). For example, if you want a random number between 3 and 20 (inclusive), use mt_rand(3, 20).

3. array_rand function

<&#63;php
$base = 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');
 
$random = '';
for ($i=0; $i < 16; $i++) { 
 $random.=$base[array_rand($base)];
}
echo $random;
&#63;> 

array_rand returns a random key value in the array, which is somewhat similar to the mt_rand() function. The rest is nothing special, just use it flexibly.

4. shuffle function

<&#63;php
$base = array('a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z','A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z','0','1','2','3','4','5','6','7','8','9');
if(shuffle($base)){
 print_r($base);
}
&#63;> 

The shuffle function is to disrupt the sequence of an array, which is a bit random. It is placed in the random function here. The return value is a bool value, which is equivalent to directly referencing the original variable.

5. str_shuffle function

<&#63;php
$base = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789';
echo str_shuffle($base);
&#63;>

The function of str_shuffle here is similar to that of shuffle. The only difference is the return value. The original string of str_shuffle remains unchanged.

6. uniqid function

<&#63;php
echo uniqid();
//54f806528172f
&#63;>

uniqid can generate unique strings, and the scope of this application can be quite wide

4. Summary
Random functions are almost the most basic functions of every language, and PHP’s support for random functions is no exception. Here we introduce the basic usage of rand, mt_rand, array_rand, shuffle, str_shuffle, and uniqid functions. More can be combined with practical applications. Use it flexibly.

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