I'm trying to make some random string in PHP with 5 letters/numbers. It's working fine but sometimes I get a shorter string.
$characterset='ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890';
$count=0;
$lenght=strlen($characterset);
$i=5; #number of characters
while($count < $i){
$num=rand(1,$lenght);
$letter=substr($characterset, $num, 1);
$string.=$letter;
$count++;
}
And strlen($string) is sometimes 4 (checked 100 records, 85 was 4 characters)
String characters, like arrays, start counting from zero. Run your code a bunch of times: in addition to sometimes getting not enough characters, notice how you never get an A in there?
$num = rand(0,$lenght-1); will do it.
As an alternative method, you could do this:
$max_b36 = str_repeat("Z",$number_of_characters);
$max_dec = base_convert($max_b36,36,10);
$rand_dec = rand(0,$max_dec);
$rand_b36 = base_convert($rand_dex,10,36);
$result = sprintf("%0".$number_of_characters."s",$rand_b36);
This method uses (potentially) big numbers though, so it will only support 5 characters (on 32-bit systems) or 12 characters (on 64-bit systems).
Personally I'd replace your entire logic with this one line wonder :
print $characters = substr(
str_shuffle('ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890'),
0,5)
);
(slightly off formatting so it fits on the screeen)
Thank you all for help, following code working great:
$characters='ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890';
$string = '';
$random_string_length = 5;
$max = strlen($characters) - 1;
for ($i = 0; $i < $random_string_length; $i++) {
$string .= $characters[mt_rand(0, $max)];
}
Is it possible to avoid the same strings? I generated 50 000 records and had 48 the same.
substrsilently returns false, if you try to get a character from a position beyond the string end ... $\endgroup$Notice: Undefined variable: stringby declaring$string = '';'just outside the loop..=operators only work properly on pre initialised variables $\endgroup$