PHP Warning in Filemtime() & Cannot modify Header information - Headers Already Sent Error

Question

With help of @James, the image generator is in fine condition. Now, there is a tiny but strange error that the image engine outputs when a file or folder is non existent . Indeed there should be an error but i'm unsure wether it sould be this one below. Here is what happens when google tries to fetch an old non existent folder/image.jpg via the imgcpu.php thumbnail generator:

[20:24:25] PHP Warning: filemtime() [<a href='function.filemtime'>function.filemtime</a>]: stat failed for old_folder/old-image.jpg in imgcpu.php on line 802
[20:24:25] PHP Warning: Cannot modify header information - headers already sent by (output started at imgcpu.php:802) in imgcpu.php on line 201

[20:26:31] PHP Warning: filemtime() [<a href='function.filemtime'>function.filemtime</a>]: stat failed for old_folder/old-image.jpg in imgcpu.php on line 802
[20:26:31] PHP Warning: Cannot modify header information - headers already sent by (output started at imgcpu.php:802) in imgcpu.php on line 201

[20:28:24] PHP Warning: filemtime() [<a href='function.filemtime'>function.filemtime</a>]: stat failed for old_folder/old-image.jpg in imgcpu.php on line 802
[20:28:24] PHP Warning: Cannot modify header information - headers already sent by (output started at imgcpu.php:802) in imgcpu.php on line 201

[20:31:03] PHP Warning: filemtime() [<a href='function.filemtime'>function.filemtime</a>]: stat failed for old_folder/old-image.jpg in imgcpu.php on line 802
[20:31:03] PHP Warning: Cannot modify header information - headers already sent by (output started at imgcpu.php:802) in imgcpu.php on line 201 

It seems that line 201 and 802 have something to do with it:

line 201**     header('HTTP/1.1 400 Bad Request');
line 202       die($message);
....
line 801       header("Content-type: " . $this->_mime);
line 802**     $last_modified = filemtime($source);

Question: Is the error correct? or should the warning be solved somehow? If so, how?

Answer 1

You should not try to get the last modification date of a file if that file doesn't exist, I suppose.

You should check whether the file exists, first, using the file_exists() function.

I suppose you should use something like this :

if (file_exists($source)) {
    $last_modified = filemtime($source);
    // Use the $last_modified variable
}
else {
    // the file doesn't exist => 404
    header('HTTP/1.1 404 Not Found');
    die;
}