Several solutions for PHP to generate unique IDs _php tips

Look up the Internet, there are a lot of ways

1, MD5 (Time (). Mt_rand (1,1000000));

This method has a certain probability that there will be repetition

2. PHP built-in function uniqid ()

The Uniqid () function generates a unique ID based on the current time in microseconds.

The W3school reference manual says: "The IDs generated through this function are not optimal because of the system time." If you want to generate an absolutely unique ID, use the MD5 () function.

The following method returns a similar result: 5ddb650f-4389-f4a9-a100-501ef1348872

Copy Code code as follows:

function uuid () {
if (function_exists (' Com_create_guid ')) {
return Com_create_guid ();
} else {
Mt_srand (Double) microtime () * 10000); Optional for PHP 4.2.0 and up. Sow the seeds casually, 4.2.0 do not need them later.
$charid = Strtoupper (MD5 (Uniqid (rand (), true)); Generates a unique ID based on the current time (in microseconds).
$hyphen = Chr (45); // "-"
$uuid = '. Chr (123)//"{"
substr ($charid, 0, 8). $hyphen. SUBSTR ($charid, 8, 4). $hyphen. SUBSTR ($charid, 12, 4). $hyphen. SUBSTR ($charid, 16, 4). $hyphen. SUBSTR ($charid, 20, 12);
. chr (125);//"}"
return $uuid;
}
}

Com_create_guid () is a PHP-generated unique ID method, after php5 seems to have gone.
3, the official uniqid () the reference manual has the user to provide the method, the result is similar: {E2DFFFB3-571E-6CFC-4B5C-9FEDAAF2EFD7}

Copy Code code as follows:

Public Function create_guid ($namespace = ' ") {
static $guid = ';
$uid = Uniqid ("", true);
$data = $namespace;
$data. = $_server[' request_time '];
$data. = $_server[' http_user_agent '];
$data. = $_server[' local_addr '];
$data. = $_server[' Local_port '];
$data. = $_server[' remote_addr '];
$data. = $_server[' Remote_port '];
$hash = Strtoupper (hash (' ripemd128 ', $uid. $guid. MD5 ($DATA)));
$guid = ' {'.
substr ($hash, 0, 8).
'-' .
SUBSTR ($hash, 8, 4).
'-' .
SUBSTR ($hash, 12, 4).
'-' .
SUBSTR ($hash, 16, 4).
'-' .
SUBSTR ($hash, 20, 12).
'}';
return $guid;
}