Fatal error: Maximum execution time of 30 seconds

<?php function resizeIMG($img) 
{ 
   $maxwidth  = 200;
   $maxheight = 200;

   $size = getimagesize($img); 

   if($size[0] > $size[1]) 
   { 
      if($size[0] > $maxwidth) 
      { 
         $width = $maxwidth; 
         $tel = $width/$size[0]*$size[1]; 
         $height= round($tel,0); 
      } 
      else 
      { 
         $width = $size[0]; 
         $height = $size[1]; 
      } 
   } 
   else 
   { 
      if($size[1] > $maxheight) 
      { 
         $height = $maxheight; 
         $tel = $height/$size[1]*$size[0]; 
         $width= round($tel,0); 
      } 
      else 
      { 
         $width = $size[0]; 
         $height = $size[1]; 
      } 
   } 
   if($size[0] < $maxwidth && $size[1] < $maxheight) 
      return '<img src='.$img.' width='.$width.' height='.$height.' />'; 

   else 
      return '<a style="cursor:" href="javascript:void(0)" onClick="window.open(\''.$img.'\', \'popup\', \'height='.$size[1].', width='.$size[0].', fullscreen=no, location=no, menubar=no, status=no, toolbar=no, scrollbars=no, resizable=no\')"><img style="border: 1px #000000 dashed;" src='.$img.' width='.$width.' height='.$height.' alt="Klik op dit plaatje om voor de ware grootte" /></a>'; 
} 

<?php function resizeIMG($img) 
{ 
   $maxwidth  = 200;
   $maxheight = 200;
 
   $size = getimagesize($img); 
 
   if($size[0] > $size[1]) 
   { 
      if($size[0] > $maxwidth) 
      { 
         $width = $maxwidth; 
         $tel = $width/$size[0]*$size[1]; 
         $height= round($tel,0); 
      } 
      else 
      { 
         $width = $size[0]; 
         $height = $size[1]; 
      } 
   } 
   else 
   { 
      if($size[1] > $maxheight) 
      { 
         $height = $maxheight; 
         $tel = $height/$size[1]*$size[0]; 
         $width= round($tel,0); 
      } 
      else 
      { 
         $width = $size[0]; 
         $height = $size[1]; 
      } 
   } 
   if($size[0] < $maxwidth && $size[1] < $maxheight) 
      return '<img src='.$img.' width='.$width.' height='.$height.' />'; 
 
   else 
      return '<a style="cursor:" href="javascript:void(0)" onClick="window.open(\''.$img.'\', \'popup\', \'height='.$size[1].', width='.$size[0].', fullscreen=no, location=no, menubar=no, status=no, toolbar=no, scrollbars=no, resizable=no\')"><img style="border: 1px #000000 dashed;" src='.$img.' width='.$width.' height='.$height.' alt="Klik op dit plaatje om voor de ware grootte" /></a>'; 
}