random 6 digit number

[pouncer]

how do i get a random 6 digit number in php guys?

[PC Nerd]

$digit_loop = 1;

$digit = '';

while ( $digit_loop <= 6){

      $digit = $digit.rand(0, 9);

}

 

echo $digit

you can check i in a loop througha database or whatever if it needs to be unique

[AndyB]

$random = rand(100000,999999);

[pouncer]

ah thanks. so php has the rand function too

 

could i just not use

 

rand(100000,999999);

 

[kenrbnsn]

Use the rand() function:

<?php
$num = rand(100000,999999);
echo $num;
?>

or

<?php
$num = sprintf("%06d",rand(1,999999)); // zero filled 6 digits
echo $num;
?>

 

Ken

[448191]

$digit_loop = 1;

$digit = '';

while ( $digit_loop <= 6){

      $digit = $digit.rand(0, 9);

}

 

echo $digit

you can check i in a loop througha database or whatever if it needs to be unique

 

Uhmm...

 

Apart from the fact that it serves no pupose, there are 3 things wrong with that code:

 

1. It results in an infinite loop.

2. It allows leading zero's, producing 'numbers' with less than 6 digits.

3. It uses a string to store an integer.

 

[PC Nerd]

well i didnt say it was perfect, but its a start, and easily fixed.

 

ive done it before, but im sure the smart people at this forum can fix it for their own sites, its not like were doing all the coding for them..........

 

its a start and a pointer, surely thats gotta help

[kenrbnsn]

3. It uses a string to store an integer.

 

Since PHP is a typeless language, this is not a bad thing as can be seen by this example:

<?php
<?php
$a = sprintf("%06d",rand(1,999999));
$b = rand(100000,999999);
echo '<pre>';
var_dump($a);
var_dump($b);
echo '</pre>';
$c = $a + $b;
echo $c;
?>

Numbers in strings are treated as numbers.

 

Ken

[obsidian]

well i didnt say it was perfect, but its a start, and easily fixed.

 

Indeed, and it's not a bad suggestion. Here's one using that idea that does work like you are intending:

<?php
$num = '';
for ($i = 0; $i < 6; $i++) {
  $num .= rand(0,9);
}
?>

 

While this isn't practical for smaller numbers that you could simply use the rand() method mentioned initially by AndyB, this could get very handy when working with random numbers that exceed the boundaries of the unsigned integer in PHP. Imagine you needed a 30-40 digit random number (or even bigger). You can't use the built-in data types, so you'd have to use something like this to do it.

[448191]

Ok, so maybe I was a bit harsh, and too hasty to dismiss string assembly as a means to generate a random number.

 

However there are still some things to consider.

 

<?php
$num = '';
for ($i = 0; $i < 6; $i++) {
  $num .= rand(0,9);
}
?>

 

That still possibly produces a string with a leading zero. With a minor ajustment one should be fine though:

 

<?php
$num = rand(1,9);
for ($i = 0; $i < 5; $i++) {
  $num .= rand(0,9);
}
?>

 

this could get very handy when working with random numbers that exceed the boundaries of the unsigned integer in PHP.

 

You could also use a float instead:

 

<?php
public function getFloat($digits){
if(is_int($digits)){
	if($digits > 308) return false;
	$this->maxValue = pow(10, $digits) - 1;
	$this->minValue = $digits == 1? 0 : pow(10, $digits) / 10; 

	do {
		$this->value = $this->minValue + $this->maxValue * mt_rand(0, pow(2,15)-1)/pow(2,15)-1;
	} while($this->value < $this->minValue || $this->value > $this->maxValue);
	return $this->value;
}
throw new Exception('RandomNumber::getFloat(): $digits must be (int)');
}
?>

 

But float also has a max length, ~1.0E+308 - 308 digits. So if you want more than 308 digits, yes, you'll need to use strings. The BCMath extension can do it too, but (aside from the fact that it also uses strings) that would be overkill imo. You can use the BCMath functions to calculate on your randomly assembled numeric string.

 

Also, (s)printf doesn't play along when you ask for something impossible:

 

<?php
printf('%d', $outOfBoundaryInt);
?>

Returns  2147483647 (max int). While an appropiate result, you might expect it to display as a float because of PHP's type juggling. printf() doesn't roll that way though.

 

You should be carefull when using numbers as strings:

 

<?php
//Very long string to represent float, close to INF
$str = '99999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999';

echo strlen($str)." digits\n"; //308 'digits'
$float = (float) $str; //Works fine, 1.0E+308
printf("%f",$float)."\n";//Messes up because not possible to represent as decimal float
printf("%e",$float)."\n";//Close enough, 1.000000e+30813

echo strlen($float)." digits\n"; //Exponential notation, 6 'digits' 

var_dump($float.'13'); //string(7) "1E+30813"
var_dump((float) $str); //float(1.0E+308)

var_dump((float) $float.'5'); //Stays string: string(7) "1E+3081"
var_dump($float.'5' + 1); //PHP: Ne comprend pas!: float(INF)
var_dump(bcadd($float.'5', 1));//Ignores invalid E: string(402) "1.0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
var_dump('1 .5' + 1); // .5 is discarded because of space: int(2)
?>

 

Anyway, to make a long story short (darn, too late ;P), be careful when treating numbers as strings.