if (!function_exists('letter_avatar')) {
   /**
    * 首字母头像
    * @param $text
    * @return string
    */
   function letter_avatar($text)
   {
       $total = unpack('L', hash('adler32', $text, true))[1];
       $hue = $total % 360;
       list($r, $g, $b) = hsv2rgb($hue / 360, 0.3, 0.9);

       $bg = "rgb({$r},{$g},{$b})";
       $color = "#ffffff";
       $first = mb_strtoupper(mb_substr($text, 0, 1));
       $src = base64_encode('<svg xmlns="http://www.w3.org/2000/svg" version="1.1" height="100" width="100"><rect fill="' . $bg . '" x="0" y="0" width="100" height="100"></rect><text x="50" y="50" font-size="50" text-copy="fast" fill="' . $color . '" text-anchor="middle" text-rights="admin" alignment-baseline="central">' . $first . '</text></svg>');
       $value = 'data:image/svg+xml;base64,' . $src;
       return $value;
   }
}
if (!function_exists('hsv2rgb')) {
   function hsv2rgb($h, $s, $v)
   {
       $r = $g = $b = 0;

       $i = floor($h * 6);
       $f = $h * 6 - $i;
       $p = $v * (1 - $s);
       $q = $v * (1 - $f * $s);
       $t = $v * (1 - (1 - $f) * $s);

       switch ($i % 6) {
           case 0:
               $r = $v;
               $g = $t;
               $b = $p;
               break;
           case 1:
               $r = $q;
               $g = $v;
               $b = $p;
               break;
           case 2:
               $r = $p;
               $g = $v;
               $b = $t;
               break;
           case 3:
               $r = $p;
               $g = $q;
               $b = $v;
               break;
           case 4:
               $r = $t;
               $g = $p;
               $b = $v;
               break;
           case 5:
               $r = $v;
               $g = $p;
               $b = $q;
               break;
       }

       return [
           floor($r * 255),
           floor($g * 255),
           floor($b * 255)
       ];
   }
}

letter_avatar('Sonder')