Several solutions for generating a unique id in php _ PHP Tutorial

Php provides several solutions to generate a unique id. I checked it online and found many methods: 1. md5 (time (). mt_rand (); this method has a certain probability that there will be duplicates. 2. the php built-in function uniqid () has been checked online based on microseconds. There are many methods.

1. md5 (time (). mt_rand (1,000000 ));

There is a probability that this method will be repeated.

2. php built-in function uniqid ()

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

W3school reference manual has one sentence: "Because the system time is based, the ID generated through this function is not the best. To generate an absolutely unique ID, use the md5 () function ".

The returned result of the following method is similar to: 5ddb417f-4389-f4a9-a100-501ef1348872.

The code is 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. no need to sow it after 4.2.0.
$ Charid = strtoupper (md5 (uniqid (rand (), true); // generate 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 the unique id method generated by php. it seems that php5 does not exist.
3. the official uniqid () reference manual has a user-provided method, the results are similar to: {E2DFFFB3-571E-6CFC-4B5C-9FEDAAF2EFD7}

The code is 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 ('ripmd128 ', $ 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;
}

Md5 (time (). mt_rand (); this method has a certain probability of repetition. 2. the php built-in function uniqid () is based on microseconds...