PHP, Structures and Functions, Fundamental Syntaxes

RANDOM NUMBERS

are numbers that occur in a sequence such that two conditions are met:

1 . the values are uniformly distributed over a defined interval or set.
2 . it is impossible to predict future values based on past or present ones.

Random numbers are important in statistical analysis and probability theory.

This function does not generate cryptographically secure values,therefore it should not be used for these purposes.

There are other functions in PHP that generate random integers for use in cryptography; such functions will be studied in the future.

mt_rand should be used instead of rand because it is much faster.

This function uses the MTRNG, Mersenne Twister Random Number:

Mersenne Twister


<?php

// FIRST DESCRIPTION 

int mt_rand ( );
            
?>


<?php

// SECOND DESCRIPTION 
 
int mt_rand (int $min, int $max );


where,


$min = the minimum integer value
                          of the numeric interval

$max = the maximun integer value
                          of the numeric interval obtained by: 
                                       mt_getrandmax = 2147483647
                       
?>

$min

The minimum integer value of the numeric interval.

$max

The maximum integer value of the numeric interval.

SOLVE ALL PROPOSED EXERCISES

NOT SOLVED YET

If possible in several versions of PHP

Especially the latest 7 and 8

Study the displayed data carefully

EXERCISE


<?php
 
$mtrd01  = mt_rand();

echo 'The generated random number 
                   for this system in this moment, is: ' . 
                                            $mtrd01 . '.<br><br>';

?>

EXERCISE


<?php

$min02 = 10;

$max02 = 20;
 
$mtrd02  = mt_rand($min02, $max02);

echo 'The random number generated for this system, 
                   within the numerical range:<br>[' . 
                         $min02 . ', ' . $max02 . '], at this point is ' . 
                                                    $mtrd02 . '.<br><br>'

?>

EXERCISE


<?php

$min03 = 0;

$max03 = mt_getrandmax();
 
$mtrd03  = mt_rand($min03, $max03);

echo 'The random number generated for this system, 
             within the numerical range:<br>[' . 
                  $min03 . ', ' . $max03 . '], at this point is ' . 
                                     $mtrd03 . '.<br><br>';

?>

EXERCISE


<?php

$min04 = PHP_INT_MIN;
// -9223372036854775808 -> 
// -> Since PHP 7.0.0 (64bit)

$max04 = PHP_INT_MAX;
// 9223372036854775807  ->
// -> Since PHP 5.0.5 (64bit)
 
$mtrd04  = mt_rand($min04, $max04);

echo 'The random number generated for this system, 
              within the numerical range:<br>[' . 
                    $min04 . ', ' . $max04 . '], at this point is ' . 
                                      $mtrd04 . '.<br><br>';

?>

EXERCISE


<?php

$min05 = (PHP_INT_MIN - 1);
// -9223372036854775809 

$max05 = (PHP_INT_MAX + 1);
// 9223372036854775808  
 
$rd05  = mt_rand($min05, $max05);

$min05a = (PHP_INT_MIN);
// -9223372036854775808 -> 
// -> Since PHP 7.0.0 (64bit)

$max05a = (PHP_INT_MAX);
// 9223372036854775807 -> 
// -> Since PHP 5.0.5 (64bit)

$rd05a  = mt_rand($min05a, $max05a);

echo 'The random number generated for this system, 
              within the numerical range:<br>[' . 
                    $min05a . ', ' . $max05a . '], at this point is ' . 
                                            $rd05a . '.<br><br>';

?>

RESULT

PHP 7.4.XX ( 64bit systems )

Warning: ...

The random number generated for this system, within the numerical range:

[-9223372036854775808, 9223372036854775807]

at this moment, the value is:
-4862817445697834864.

This is a particular result.
For each new run a new value will be generated.

PHP 8.0.XX ( 64bit systems )

Fatal error: ...