Php-mysql Course

To get a random number in PHP, you can use the mt_rand() function (there is also rand() function, but, according to PHP documentation, mt_rand() is faster).
- Example:
$nr = mt_rand();
echo $nr;

• To get a random number between a minimum and maximum number, use this syntax:   mt_rand($min, $max).
$nr = mt_rand(1000, 9999);
echo $nr;

Random numbers from array

If you have an array of numbers, and you want to get an random number from that array, you can use the array_rand() function. This function returns the key for a random entry.
- Example:
$nrs = array(123, 567, 4556, 34245, 78);
$rk = array_rand($nrs);
$nr = $nrs[$rk];
echo $nr;       // 4556

• If you want to pick more than one random key from array, add a seccond argument that specifies the number of keys (less than the number of elements of that array). In this case, array_rand($array, $nrk) will return an array with $nrs number of random keys from $array.
$nrs = array(123, 567, 4556, 34425, 78, 789);
$rks = array_rand($nrs, 2);     // contains 2 random keys (2, 5)

echo $nrs[$rks[0]];      // 4556
echo $nrs[$rks[1]];      // 789

Random number with distinct digits

If you want to get a random number between a minimum and maximum number, but with distinct digits, without repeated character in the random number, you can use the following function.
<?php
// returns a random number between $min and $max, with distinct digits
function getDistinctNr($min, $max) {
 // random number with distinct digits ( https://coursesweb.net )
  $nrstr = (string) mt_rand($min, $max);     // get random number, converted into string
  $n_nr = strlen($nrstr);           // number of characters
  $setnr = array();           // to store distinct digits that will form the returned number

  // traverse the characters of $nrstr to add in $setnr only its distinct digits
  // if number already in $setnr, traverse 0 to 9 to define another distinct number
  for($i=0; $i<$n_nr; $i++) {
    if(!in_array($nrstr[$i], $setnr)) $setnr[] = $nrstr[$i];
    else {
      for($i2=0; $i2<10; $i2++) {
        if(!in_array($i2, $setnr)) {
          $setnr[] = $i2;
          break;
        }
      }
    }
  }

  return implode('', $setnr);
}

// Test
$nr = getDistinctNr(1000, 9999);
echo $nr;
?>

Daily Test with Code Example

HTML
CSS
JavaScript
PHP-MySQL
Which attribute is used in <a> tag for the address of the link?
src href rel
<a href="http://coursesweb.net/" title="CoursesWeb.net">CoursesWeb.net</a>
Which CSS property sets the type of the text font?
font-family text-decoration font-size
h2 {
  font-family:"Calibri",sans-serif;
}
What instruction selects all the <div> tags with class="cls"?
querySelector("div.cls") getElementsByTagName("div") querySelectorAll("div.cls")
var elm_list = document.querySelectorAll("div.cls");
var nr_elms = elm_list.length;       // number of selected items
alert(nr_elms);
Indicate the function that can be used to get the sum of values in an array.
array_sum() array_diff() array_shift()
$arr =[1, 2, 3, 4);
$arr_sum = array_sum($arr);
echo $arr_sum;       // 10
Random numbers in PHP

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