Put the value of for loop inside array

Question

I am trying to reate an array that contains all the odd numbers between 1 to 20,000. I Use the var_dump() at the end to display the array values without using loops.

For some reason it won't work out.

here's my code so far:

$array_variable = array();

for($i=1; $i<=20000; $i++){
    if($i%2 == 1){ // if the remainder after division `$i` by 2 is one{
        print_r($array_variable[$i]); // if odd, echo it out and then echo newline for better readability;
    }
}

var_dump($array_variable);

You're trying to display it without loops, but display it in your `for` loop anyway? Also, why are you trying to access `$array_variable[$i]` in an empty array before adding anything in? — Huey, Jul 01 '15 at 14:34

score 9 · Answer 1 · answered Jul 01 '15 at 14:33

You need to push the values to your array first:

$array_variable = array();
for($i=1; $i<=20000; $i++){
   if($i%2 == 1){ 
       $array_variable[] = $i;// or array_push($array_variable, $i);
   }
}
var_dump($array_variable);

Otherwise your array stays empty.

score 5 · Answer 2 · answered Jul 01 '15 at 14:33

This results in alot of undefined indexes because you're not adding anything to $array_variable.

Change the code to this:

   $array_variable = array();

    for($i=1; $i<=20000; $i++){
      if($i%2 == 1){ // if the remainder after division `$i` by 2 is one{
        $array_variable[] = $i; // $array_variable[] means adding something to the array
      }
    }

    var_dump($array_variable); //dump all odd numbers

For better readability of the array you could use:

echo "<pre>";
print_r($array_variable);
echo "</pre>";

score 0 · Answer 3 · answered Jul 01 '15 at 14:36

0

Your $array_variable is empty because you never add any elements to it. Try this instead:

$array_variable = range(1, 20000, 2);

answered Jul 01 '15 at 14:36

unfairhistogram

186
9

range() is a PHP function that generates an array if you give it the start value, the end value, and optionally the increment step. See also http://php.net/manual/en/function.range.php – unfairhistogram Jul 01 '15 at 15:47

score 0 · Answer 4 · answered Jul 01 '15 at 14:48

$array_variable = array();

for($i=1; $i<=20000; $i++){
  if($i%2 == 1){ // if the remainder after division `$i` by 2 is one{
      array_push($array_variable, $i); //Push the variable into array
  }
}

var_dump($array_variable); //dump all odd numbers

score 0 · Answer 5 · edited May 23 '17 at 11:43

You are trying to print an element it does not exist since the array is empty. If you insist on using an array use this code, you notice you assign a value to the array elements: ( and also if you want to display it on a new line in browser, use echo commented out): (if interested about more: what is the difference between echo and print_r

<?php 

        $array_variable = array();

        for($i=1; $i<=20000; $i++){
            $array_variable[$i]=$i;//assignment
            if($i%2 == 1){ // if the remainder after division `$i` by 2 is one{
            print_r($array_variable[$i]); // if odd, echo it out and then echo newline for better readability;
            //echo $array_variable[$i].'<br>';
        }
    }

        var_dump($array_variable);
    ?>

Put the value of for loop inside array

5 Answers5