Function to make a line with random fading:
<?php
function fading_line($img,$sx,$sy,$ex,$ey){
$r=rand(0,5);$g=rand(0,5);$b=rand(0,5);
$l=sqrt((($ex-$sx)*($ex-$sx))+(($ey-$sy)*($ey-$sy)));
for($i=0;$i<$l;$i++){
$a = array(255-((255/$l)*$i), 255,0,(255/$l)*$i/2,(255/$l)*$i,(255-((255/$l)*$i))/2);
$style[]=imagecolorallocate($img,$a[$r],$a[$g],$a[$b]);
}
imagesetstyle($img,$style);
imageline($img,$sx,$sy,$ex,$ey,IMG_COLOR_STYLED);
}
fading_line($img,10,20,490,40); // image, start x, start y, end x, end y
?>