PHP- Notice: Undefined offset: 1

Question

I have this code that converts numbers into words. I found it on a website (I can't remember the site). The code often works well but in numbers whose tens are 1 or 0 get this error:

Notice: Undefined offset: 1 in C:\xampp\htdocs\...\printreceipt.php on line 103.

Also numbers after the decimal are not correct. I tried very hard to modify the code to solve the problem but I have not yet solved it. Also, I have found some questions in stakoverflow with same title but there is no such code, I tried to solve my problem from the answers of those questions.

Some results of my code:

154.000 = One Hundred Fifty Four Dollar.

615.000 = Notice: Undefined offset: 1 in .. Six Hundred Five Dollar/s

545.152 = Five Hundred Forty Five Dollar/s and Fifteen Sent This is the function code:

function numtowords($num){ 
$decones = array( 
            '01' => "One", 
            '02' => "Two", 
            '03' => "Three", 
            '04' => "Four", 
            '05' => "Five", 
            '06' => "Six", 
            '07' => "Seven", 
            '08' => "Eight", 
            '09' => "Nine", 
            10 => "Ten", 
            11 => "Eleven", 
            12 => "Twelve", 
            13 => "Thirteen", 
            14 => "Fourteen", 
            15 => "Fifteen", 
            16 => "Sixteen", 
            17 => "Seventeen", 
            18 => "Eighteen", 
            19 => "Nineteen" 
            );
$ones = array( 
            0 => " ",
            1 => "One",     
            2 => "Two", 
            3 => "Three", 
            4 => "Four", 
            5 => "Five", 
            6 => "Six", 
            7 => "Seven", 
            8 => "Eight", 
            9 => "Nine", 
            10 => "Ten", 
            11 => "Eleven", 
            12 => "Twelve", 
            13 => "Thirteen", 
            14 => "Fourteen", 
            15 => "Fifteen", 
            16 => "Sixteen", 
            17 => "Seventeen", 
            18 => "Eighteen", 
            19 => "Nineteen" 
            ); 
$tens = array( 
            0 => "",
            2 => "Twenty", 
            3 => "Thirty", 
            4 => "Forty", 
            5 => "Fifty", 
            6 => "Sixty", 
            7 => "Seventy", 
            8 => "Eighty", 
            9 => "Ninety" 
            ); 
$hundreds = array( 
            "Hundred", 
            "Thousand", 
            "Million", 
            "Billion", 
            "Trillion", 
            "Quadrillion" 
            ); //limit t quadrillion 
$num = number_format($num,2,".",","); 
$num_arr = explode(".",$num); 
$wholenum = $num_arr[0]; 
$decnum = $num_arr[1]; 
$whole_arr = array_reverse(explode(",",$wholenum)); 
krsort($whole_arr); 
$rettxt = ""; 
foreach($whole_arr as $key => $i){ 
    if($i < 20){ 
        $rettxt .= $ones[$i]; 
    }
    elseif($i < 100){ 
        $rettxt .= $tens[substr($i,0,1)]; 
        $rettxt .= " ".$ones[substr($i,1,1)]; 
    }
    else{ 
        $rettxt .= $ones[substr($i,0,1)]." ".$hundreds[0]; 
        $rettxt .= " ".$tens[substr($i,1,1)]; 
        $rettxt .= " ".$ones[substr($i,2,1)]; 
    } 
    if($key > 0){ 
        $rettxt .= " ".$hundreds[$key]." "; 
    } 

} 
$rettxt = $rettxt." Dollar/s";

if($decnum > 0){ 
    $rettxt .= " and "; 
    if($decnum < 20){ 
        $rettxt .= $decones[$decnum]; 
    }
    elseif($decnum < 100){ 
        $rettxt .= $tens[substr($decnum,0,1)]; 
        $rettxt .= " ".$ones[substr($decnum,1,1)]; 
    }
    $rettxt = $rettxt." Sent"; 
} 
return $rettxt;
} 

The error of tens 1 and 0 is in the following part:

else{ 
        $rettxt .= $ones[substr($i,0,1)]." ".$hundreds[0]; 
        $rettxt .= " ".$tens[substr($i,1,1)]; 
        $rettxt .= " ".$ones[substr($i,2,1)]; 
    }

and I think and I'm not sure, the error of the decimal is in the following lines:

if($decnum > 0){ 
    $rettxt .= " and "; 
    if($decnum < 20){ 
        $rettxt .= $decones[$decnum]; 
    }
    elseif($decnum < 100){ 
        $rettxt .= $tens[substr($decnum,0,1)]; 
        $rettxt .= " ".$ones[substr($decnum,1,1)]; 
    }
    $rettxt = $rettxt." Sent"; 
} 

Answer 1

foreach ($whole_arr as $key => $i) {
    if ($i < 20) {
        $rettxt .= $ones[$i];
    } elseif ($i < 100) {
        $rettxt .= $tens[substr($i, 0, 1)];
        $rettxt .= " " . $ones[substr($i, 1, 1)];
    } else {
        $rettxt .= $ones[substr($i, 0, 1)] . " " . $hundreds[0]; //fix here
        if(substr($i, 1, 1) != 1){
            $rettxt .= " " . $tens[substr($i, 1, 1)];
            $rettxt .= " " . $ones[substr($i, 2, 1)];
        }
        else{
            $rettxt .= " " . $ones[substr($i, 0, 1)+9];
        }

    }
    if ($key > 0) {
        $rettxt .= " " . $hundreds[$key] . " ";
    }
}