I use php scripts to generate file names. So it is essential for me 
that php runs if I want to use router as a webserver to display thumbnails of the pics in the folder

https://forum.openwrt.org/viewtopic.php?pid=46617

opkg install lighttpd lighttpd-mod-cgi php5 php5-cgi

http://192.168.0.5:81/phpinfo.php



/etc/lighttpd/lighttpd.conf 


--------------------------------
error need to have
Right after
#cgi.assign = ( ".pl" => "/usr/bin/perl", ".cgi" => "/usr/bin/perl" )

add
cgi.assign = ( ".php" => "/usr/bin/php-cgi" )
but this was wrong, and did not work

--------------

correct solution 
opkg install opkg install php4 php4-cgi


http://192.168.0.5:81/index.php



==========================================================================
php code that checks all files in a directory, 
selects all jpgs and generates webpage with thumbnails.
---------------------------------------------------------------------
 
<?php
#echo getcwd() . "\n";

#$path = "/home/u230912284/public_html/old/";
$path = getcwd();
$folder1 = opendir($path) or die("Unable to open folder");

while (false !== ($file = readdir($folder1))) 

{
 
if($file == "ind.php")
 continue;
 
if($file == "index.html")
 continue;
 
if($file == ".")
 continue;
 
if($file == "..")
 continue;

 
$afile[]=$file;
 
rsort($afile);
 
$anz=count($afile);

}
closedir($folder1);

for($i=0;$i<$anz;$i++)
  {
  
  
$file=$afile[$i];

#  $file="http://jugla.freezoka.net/old/".$afile[$i];
echo "<A HREF='$file'><img src='$file' width=160 height=120 alt='$file'></A>";

  
}