Algorithm for efficient random extraction of specified records from arrays in PHP_PHP Tutorial

PHP uses the array array_rand() function to efficiently randomly extract a specified number of records. It can randomly extract records in the database and is suitable for random display and lottery programs.

This algorithm mainly uses the array_rand() function of PHP. Let’s take a look at the main functions of the array_rand() function:

array_rand—randomly remove one or more cells from the array

mixed array_rand(array $input[,int $num_req] )

array_rand() is useful when you want to remove one or more random cells from an array. It accepts input as an input array and an optional parameter num_req, which specifies how many cells you want to remove - if not specified, it defaults to 1.

If you only take out one, array_rand() returns the key name of a random unit, otherwise it returns an array containing random key names. This way you can randomly pull out keys and values ​​from the array.

Let’s take a look at a small example:

Copy code The code is as follows:

srand((float) microtime() * 10000000) ;
$input = array("Neo", "Morpheus", "Trinity", "Cypher", "Tank");
$rand_keys = array_rand($input, 2);
print $input [$rand_keys[0]] . "n";
print $input[$rand_keys[1]] . "n";
?>

This function will randomly select the record number in the $list array. If you need to record the content, you only need to output it.

The following is an example of randomly selecting specific records from the database:

Copy code The code is as follows:

$list = $DB->where(" status=1 and flag=1")->order('sort')->select();
unset($Case);
$count = count($list);
$ rand_list=range(0, $count-1);
$rand_list = array_rand($rand_list, 10);
$tuijian_array = array();
foreach ($rand_list as $key) {
$tuijian_array[] = $list[$key];
}
unset($case_list);
print_r($tuijian_array);
?>

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