ファイル内の行数を調べる

--------------------------------------------------- 
$c=0;
 $fp = fopen("index.html","r");
 while($d = fgets($fp,1)){$c++;}
 fclose($fp);
--------------------------------------------------- 

--------------------------------------------------- 
$c = count(file('index.html'));
--------------------------------------------------- 

--------------------------------------------------- 
exec("wc -l index.html",$c);
--------------------------------------------------- 

どれが早い？