<?php if ($_POST['email']) { /* check whether the file is loading from the post and assign values to the variables */
$firstname=$_POST['firstname'];
$lastname=$_POST['lastname'];
$email=$_POST['email'];
$address=$_POST['address'];
$telephone=$_POST['telephone'];
$countfile = "/cgi-bin/countforms.bcnt"; /* define the file containing the count */
$outfile = "/cgi-bin/outputforms.csv"; /* define the file containing the form data, in this case a .csv text file containing 1 row of each form submitted */
$form_id = file_get_contents( $file ) + 1; /* read the last form number and increment */
$fp = fopen($file, 'w'); /* open the couint file and erase the contents */
fputs ($fp, sprintf('%06d',$form_id));  /* put the new count number to the count file
fclose($fp);
$fo = fopen($outfile,'a+'); /* open the output file to append the new data to the end /*
fputs ($fo, "$form_id,$firstname,$lastname,$email,$address,$telephone\n"); /* write the form to the output file */
fclose($fo);
}
else {
$firstname=$lastname=$email=$address=$telephone=" "; /* blank all data fields */
$form_id='id will be generated on submission'; /* information prompt */
}  ?>
<form action='<?php echo $_SERVER['PHP_SELF']; ?>' method='post'>
<div>ID= <?php echo $form_id." Please record this number for your records"; ?></div>
Firstname <input type=text name='firstname' value="$firstname" />
Lastname <input type=text name='lastname' value="$lastname" /><br />
Email <input type=text name='email' value="$email" />
Address <input type=text name='address' value="$address" /><br />
telephone <input type=text name='telephone' value="$telephone" /><br />
<?php if (!S_POST['email']) {echo "<input type='submit' name='submit' value='submit' />" ;} else { echo "thank you";  }
</form> <!-- normal html form -->

	$fc =fopen("reg_ctr.txt","a+") or die("Error!");
	flock($fc,LOCK_EX);			/* lock the file */
	$seq_ctr = fread($fc,10);
	$seq_ctr_next = $seq_ctr;
 	@$seq_ctr_next = $seq_ctr_next+1;
	ftruncate($fc,0);
	$ret=fwrite($fc,$seq_ctr_next);
	fflush($fc);
	flock($fc,LOCK_UN);                               /* unlock the file */
	$ret=fclose($fc);

$form_id = file_get_contents( $countfile ) + 1;

$i=0;
$rand_no="";
while($i<6)
{
	$rand_no=$rand_no.rand(0,9);
       $i++;
}
echo "6 digit random no.".$rand_no;
 
I hope this code may help you
Thanks 
Tulsa

$rand_no = rand(0,9).rand(0,9).rand(0,9).rand(0,9).rand(0,9).rand(0,9);
echo $rand_no

function random_zfill() {
    $int = mt_rand(0,999999);
    for($i=0; $i<(6-strlen($int)); $i++)$zeroes .= '0';
    return $zeroes.$int;
}
 
$my_number = random_zfill();