Create png letter icon with PHP

create_icon.php

<?php
function create_icon($first_letter, $second_letter, $save_as)
{
    $image = ImageCreate(64, 64) or die ("Error making image");//Make the base image (64 x 64)
    $background_color = ImageColorAllocate($image, rand(0, 255), rand(0, 255), rand(0, 255));//Base image background color (random)
    $text_color = ImageColorAllocate($image, 255, 255, 255);//White text for font
    $font = '/var/www/html/ariel.ttf';//Defined font file
    if ($second_letter == ''){//Positioning for one vs two letters
        $string = "$first_letter";
        $img = imagettftext($image, 36, 0, 17, 47, $text_color, $font, $string);
    } else {
        $string = "$first_letter".$second_letter."";
        $img = imagettftext($image, 36, 0, 4, 47, $text_color, $font, $string);
    }
    $img = Imagepng($image, $save_as);//Finish the image generation
    imagedestroy($image);//Clear memory?
    return true;
}
create_icon('L', 'S', 'icon.png');//Create an icon
echo "<img src='icon.png'>";//Show it