Arithmetic questions about arrays in PHP

1. The write function creates an array of length 10, the elements in the array are incrementing odd numbers, and the first item is 1.

function Createarr ($first, $length) {
for ($i = $first; $i <= $length; $i + +) {
$num = $i-1;
$arr [] = $num;
}
return $arr;
}
Print_r (Createarr (1,10));

2. Create an array of length 10, the number in the array is an increment of the equal number, the ratio is 3, the first item is 1.

function Createarr ($ratio, $length) {
$num = 1/$ratio;
for ($i =1; $i <= $length; $i + +) {
$num = $num * $ratio;
$arr [] = $num;
}
return $arr;
}
Print_r (Createarr (3,10));

3. Find the subscript for the largest number in the array.

function Maxkey ($arr) {
$maxval = max ($arr);
foreach ($arr as $key = = $val) {
if ($maxval = = $val) {
$maxkey = $key;
}
}
return $maxkey;
}


$arr = Array (0,-1,-2,5,15,3);
echo Maxkey ($arr);

4. Create an array of length 10, and the elements in the array satisfy the law of the Fibonacci sequence.

function Arrfibo ($n) {
for ($i =0; $i < $n; $i + +) {
if ($i <2) {
$arr [$i] = 1;
}else{
$arr [$i] = $arr [$i-1] + $arr [$i-2];
}
}
return $arr;
}
Print_r (Arrfibo (8));

5. Write a method that intercepts the last 5 items of an array longer than 10, without changing the order into the first 5 items, such as {1,2,3,4,5,6,7,8,9,10} to {6,7,8,9,10,1,2,3,4,5}.

function Arrsort ($arr) {
$num = count ($arr);
if ($num > 10) {
Array_slice ($arr, starting position, capturing length, preserving index (default = False))
$arr _firstpart = array_slice ($arr, 0, $num -5,true);
$arr _lastpart = Array_slice ($arr, ($num-5), 5,true);
}else{

echo "Array no more than 10 elements, please re-enter";
Exit ();
}
Stitching
$arr _new = Array_merge ($arr _lastpart, $arr _firstpart);
return $arr _new;
}
$arr = Array ("A" =>1,2,3,8,9,6, "B" =>5,-1, "C" =>8,0,7);
echo "<pre>";
Print_r ($arr);
echo "<br>= = = = = =" after stitching = = = = <br><br> ";
Print_r (Arrsort ($arr));
echo "</pre>"; 6. Concatenate two arrays into a new array.$arr = Array ("A" =>1, "B" =>2,3);
$arr 2 = Array ("a" =>dee,3,5);
$arr 3 = Array_merge ($arr, $arr 2);
$arr 4 = array_merge_recursive ($arr, $arr 2);
echo "<pre>";
Print_r ($arr 3);
echo "<br> = = = = = <br><br>";
Print_r ($arr 4);
echo "</pre>";

7. Connecting two arrays into a new array

$arr = Array ("A" =>1, "B" =>2,3);
$arr 2 = Array ("A" = "Zou", 3,5);
$arr 3 = Array_merge ($arr, $arr 2);
$arr 4 = array_merge_recursive ($arr, $arr 2);
echo "<pre>";
Print_r ($arr 3);
echo "<br> = = = = = <br><br>";
Print_r ($arr 4);
echo "</pre>";

8. Reverse array (cannot use Rsort function, cannot generate new array)

$arr = Array ("A", "B", "C", 1,10);
$i = "";//subscript to replace the number of positions
$j = "";//temporary variable
$k = "";//subscript of the number of locations to be replaced
$len = count ($arr);
$half _len = Floor ($len/2);//down rounding, the value of rounding is the number of loops
for ($i =0; $i < $half _len; $i + +) {
    $j = $arr [$i];    
   //Judgment array count parity
    if ($len%2!=0) {//odd
    
        $k = $half _len*2-$i;
   }else{      &NBSP
       //even
        $K = $half _len*2-$i-1;
   }
    $arr [$i] = $arr [$k];
    $arr [$k] = $j;
}
Echo "<pre>";
Print_r ($arr);
echo "</pre>";

9.PHP Digital amount converted to size format function Daxie ($num) {
$da _num = Array ("0", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine");
$str = ";
if (Is_numeric ($num) && strlen ($num) >0) {
for ($i =0; $i <strlen ($num); $i + +) {
$str. = $da _num[substr ($num, $i, 1)];
}
}
return $str;
}
Echo Daxie (1896);

Arithmetic questions about arrays in PHP