Remove multiple whitespaces

<?php

$str = "I      am a good  boy";
$str_length = strlen($str);
$str_arr = str_split($str);
for ($i = 0; $i < $str_length; $i++) {
    if (isset($str_arr[$i + 1])
        && $str_arr[$i] == ' '
        && $str_arr[$i] == $str_arr[$i + 1]) {
        unset($str_arr[$i]);
    } else {
        continue;
    }
}

echo implode("", $str_arr);

?>

Leap Year Programming

<?php

$year = 2020;
if(($year % 4 == 0) && ($year % 100 !=0) or ($year %400 == 0))
{
    echo $year." Is leap year";
}
else
{
    echo $year ." is not a leap year";
}

?>

Fibonacci Sequence in PHP

<?php

$num =20;

$a = 0;

$b = 1;

echo $a."</br>";

echo $b."</br>";

for($i = 1; $i <= $num; $i++)

{

    $c = $a+$b;

    echo $c."</br>";

    $a = $b;

    $b = $c;

}

?>

Sorting Array without sorting function in PHP

<?php

$array=array(8,4,9,11,2);

for($i=0;$i < count($array);$i++)
{
    for($j=0;$j < $i;$j++)
    {
        if($array[$i] < $array[$j])
        {
            $temp=$array[$i];
            $array[$i]=$array[$j];
            $array[$j]=$temp;
        }
    }
}
print_r($array);

?>