How automatically generate new random value in textbox if the value already exist in database?
This is my example of my code.
<?php
$length = 1;
$randomString = substr(str_shuffle("123456789"), 0, $length);
$mysqli1 = new mysqli("localhost", "root", "", "k");
$sql = $mysqli1->query("SELECT catid FROM subcat WHERE catid = '$randomString'");
if(($sql->num_rows) > 0){
echo "User id exists already.";
}
echo '<input name="id" value="'.$randomString.'">';
?>
Thanks for advanced!
use this strtotime('now')
From W3schools : strtotime parses an English textual datetime into a Unix timestamp (the number of seconds since January 1 1970 00:00:00 GMT).
This will always be unique.So there wont be any check needed.
Just in case if two user come simutaneously at a time,
Append a random string..for example:
$unique_id=strtotime('now')."".substr(str_shuffle("abcdefghijklmnopqrstuvwxyz"), 0, 5);
Clearly, you need an unique value
The uniqid() function generates a unique ID based on the microtime (current time in microseconds).
echo uniqid();
Edit: The OP want only 6 characters. So try something like
$id = uniqid();
$id = substr($id,rand(0,strlen($id) - 6),6);
This will be better, you can try this
$randomString = md5(uniqid(rand(), true));
A somewhat decently random string can be generated with this (Linux example):
substr(sha1(openssl_random_pseudo_bytes(3)), 0, 6);
Nonetheless, duplicates may occur due to the limited value domain; the following algorithm typically works:
"INSERT IGNORE".Generate it again.
<?php
$length = 1;
$randomString = substr(str_shuffle("123456789"), 0, $length);
$mysqli1 = new mysqli("localhost", "root", "", "k");
$sql = $mysqli1->query("SELECT catid FROM subcat WHERE catid = '$randomString'");
if(($sql->num_rows) > 0){
$randomString = substr(str_shuffle("123456789"), 0, $length);
}
echo '<input name="id" value="'.$randomString.'">';
?>
Or add a time at the end of the generated string to make it more random.
Something like this, and you should have a bigger length value. Because with length one, you can't have more random numbers.
substr(str_shuffle("123456789"), 0, $length).time();
But still there is chance of repeating unless you make a better algorithm using md5 or something.