Better default avatars

create_avatar.php

<?php
/**
 * Creates nicer default avatars
 * by using first initial on flat color
 * 
 * How to:  echo create_avatar( 'yurivictor', 48 );
 * Example: http://yurivictor.com/avatars
 *
 * @var string $user, the name of the user to create the avatar
 * @var int $size, the size in px of the avatar
 * @uses array_rand()
 * @uses substr()
 * @return html of avatar
 */
function create_avatar( $user, $size ) {

    // Colors from http://flatuicolors.com/
    $colors = array( 
        '#1abc9c',
        '#2ecc71',
        '#3498db',
        '#9b59b6',
        '#34495e',
        '#16a085',
        '#27ae60',
        '#2980b9',
        '#8e44ad',
        '#2c3e50',
        '#f1c40f',
        '#e67e22',
        '#e74c3c',
        '#f39c12',
        '#d35400',
        '#c0392b',
    );

    // Get random color
    $random_color = array_rand($colors, 2);
    $random_color = $colors[$random_color[0]];

    // Get first letter of user
    $first_letter = substr( $user, 0, 1 );

    // Create size CSS
    $font_size = $size / 3 * 2;
    $size_css = 'font-size: ' . $font_size . 'px; height: ' . $size . 'px; line-height: ' . $size . 'px; width: ' . $size . 'px;';

    return '<div class="avatar" style="background-color: ' . $random_color . '; color: #fff; text-align: center; text-transform: uppercase; ' . $size_css . '">' . $first_letter  . '</div>';

}