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Manual: rand
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rand

(PHP3 , PHP4 )

rand -- Generate a random value

Description

int rand ([int min [, int max]])

If called without the optional min, max arguments rand() returns a pseudo-random value between 0 and RAND_MAX. If you want a random number between 5 and 15 (inclusive), for example, use rand (5, 15).

Remember to seed the random number generator before use with srand().

Megjegyzés: In versions before 3.0.7 the meaning of max was range. To get the same results in these versions the short example should be rand (5, 11) to get a random number between 5 und 15.

See also srand(), getrandmax(), mt_rand(), mt_srand(), and mt_getrandmax().


User Contributed Notes: rand

j@avias.com
03-Sep-1998 07:46
>Returns a pseudo-random value between
>0 and RAND_MAX. If you want a random
>number between 5 and 15, for example,
>use rand()%10 + 5.
May be between 5 and 14?

PS thks for php!



zkimmel@earthlink.net
10-May-1999 04:43
On win32, at least, the second input to rand() seems to be EXCLUSIVE, not inclusive.

rand(0,2) => gives a number from 0 to 1
rand(0,3) => gives a number from 0 to 2



m.stolte@samhoud.nl
16-Dec-1999 07:57
srand doesn't seem to be needed, since using only rand(1,5); returns random values too....

Maarten Stolte

cybin@whid.net
24-Dec-1999 03:42
srand() is needed... at least on my apache server. without seeding the random generator, it always chose 1. a good seed to use (from the srand() page)

srand((double)microtime()*1000000);



xssiv@NOSPAM.theglobe.com.SPAMNO
28-Jan-2000 01:20
Seems that both min and max values are needed (3.0.14). So:
<PRE>
&lt;?
srand((double)microtime()*1000000);
echo "rand(1,99)";
?>
</PRE>

joestump98@yahoo.com
02-Feb-2000 01:10
Seeding the random number is definately required. If you want to pull a random record from a MySQL database try the following it worked for me on www.miester.org for my quotes database.

&lt;?php
//remember to connect to you DB as usual
$sql = "SELECT * FROM table";
$result = mysql_query($sql);

//return number of records
$nums = mysql_num_rows($result);

//seed the random number
srand((double)microtime()*1000000);
$random = rand(5,15);

//now select the random record
$sql = "SELECT * FROM table WHERE id='$random'";
$result = mysql_query($sql);

//bring random record into $myrow array
$myrow = mysql_fetch_array($result);

//now just echo it using $myrow[] pattern

?>

matthewjetthall@newhmw.com
07-Mar-2000 02:04
Here's a bit of code I use in an include file to generate a random record from a mySQL database that has an ID field and one other field. Contact me with questions.

&lt;?php
// =-=-=-=--=-=-=-=-=-=--=-=-=-=-=--=-=-=-=-=-=--=-=-=-=-=--=-=-=-=-=-=--=-=
//This code should be included in a file needing a random number function
//Include file for Random Number and SQL Row Generator
//Matthew Jett Hall -- www.newhmw.com -- Tuesday, 7, March, 2000 at 01:04:04
//matthewjetthall@newhmw.com / www.tastylinux.com
// =-=-=-=--=-=-=-=-=-=--=-=-=-=-=--=-=-=-=-=-=--=-=-=-=-=--=-=-=-=-=-=--=-=
// $long_seed = the seed for the random number
// $str_tableName = the name of the table upon which to perform the random generation
// =-=-=-=--=-=-=-=-=-=--=-=-=-=-=--=-=-=-=-=-=--=-=-=-=-=--=-=-=-=-=-=--=-=
function randomNumber($long_seed) {
// seed with microseconds since last "whole" second
srand((double)microtime()*1000000);
$randval = rand(1,$long_seed);
return($randval);
}
function randomItem($str_tableName) {
//get a random item from the table based upon the table count
require('db.inc'); //connect to the database
//get the number of records in the database
$str_SQL='select * from ' . $str_tableName;
$result=mysql_query($str_SQL); //check the # of records
$int_numberOfRows = @mysql_num_rows($result); //count how many records there are
//select a single record based upon a random # generated from the row count
$str_SQL='select * from ' . $str_tableName . ' where ID='. randomNumber($int_numberOfRows);
$result=mysql_query($str_SQL);
while ($myrow=mysql_fetch_row($result)){
$hold=$myrow[1];
}
return($hold);
}
?>

tomber@vinp.de
12-Apr-2000 06:07
What about the following for a 10 Digit Number: rand(1000000000,9999999999); If you use this way you actually never have any 0 as the first number, but you always have a 10digit number.

online-caesar@geocities.com
13-Jul-2000 06:05
I am using PHP4 and it seems that rand and srand are not supported in classes.

ominousone@home.com
24-Jul-2000 04:00
It appears 4.0.1+ has a problem with rand()s when supplied with arguments above 9999. For instance:

$foo = rand(1,9999); # fine
$foo = rand(1,99999); # error

whoisthisfreak@bigfoot.com
12-Aug-2000 02:39
I have found a better and more reliable way of getting a random record from an sql database with php. Methods that I had found on the Internet forced you to linearly cycle through records until you reached a suitably random one. Other methods required you to have a consecutively numbered index field in the table. Although most tables DO have numerical indexes, sometimes the numbers are not consecutive. This is what I came up with:

function randomrec($table, &$row, $db)
{

$sql = "SELECT * FROM $table";
$result = mysql_query($sql, $db);
$numrecs = mysql_num_rows($result);
srand((double)microtime()*1000000);
$recnum = rand(0, $numrecs-1);
$sql = "SELECT * FROM $table LIMIT $recnum, 1";
$result = mysql_query($sql, $db);
$row = mysql_fetch_array($result);

}

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