Wenn text vorhanden dann ersetzen

$file_handle = fopen("test.csv", "r");
while (!feof($file_handle) ) {
$line_of_text = fgetcsv($file_handle, 1024);
$rep = str_replace("$line_of_text", "ok", "korrekt");
print $rep;
}
fclose($file_handle);

<?PHP
$file = "test.csv"; 
$file_inhalt = file_get_contents($file); 
$file_inhalt = str_replace("ok","korrekt",$file_inhalt);
$fp = fopen ($file,"r");
fwrite($fp,$file_inhalt);
fclose($fp); 
echo $file_inhalt;
?>