PHP serial number generation function and string replacement function code

I'm glad to have two functions that are useful to you. The first one is used to generate the serial number. The second one is used to encrypt some strings. modify it a little bit, you can find the effect of some hidden characters such as itb ********* @ gmail.com that we often see when retrieving the password. The code is as follows:
/**
* Serial number generator
*/
Function snMaker ($ pre = ''){
$ Date = date ('ymmd ');
$ Rand = rand );
$ Time = mb_substr (time (), 5, 5, 'utf-8 ');
$ SerialNumber = $ pre. $ date. $ time. $ rand;
// Echo strlen ($ serialNumber ).'
';
Return $ serialNumber;
}
Echo snMaker ();
/**
* Replace a part of a string with a specific character.
* @ Param str or int $ str string to be processed
* @ Param str or int $ to replace the string
* @ Param int $ start keep the first few characters
* @ Param int $ end keep the last few characters
*/
Function hideString ($ str = 'hello', $ to = '*', $ start = 1, $ end = 0 ){
$ Lenth = strlen ($ str)-$ start-$ end;
$ Lenth = ($ lenth <0 )? 0: $ lenth;
$ To = str_repeat ($ to, $ lenth );
$ Str = substr_replace ($ str, $ to, $ start, $ lenth );
Return $ str;
}
Echo hideString ();