is_writable() is lying to me

[Peter]

Very perplexing. This function creates a png image of a random string (this
is to filter out blogging spam). It should be very straight forward.
function createImage( $text=0 )
{
$img_dir = '/tmp';

(snip!)

$filename = "$img_dir/" . randomString(12) . '.png';

if ( ! is_writable($filename) )
echo ("Can't write to $filename<br>");

ImagePNG( $image, $filename );
ImageDestroy( $image );

return array(
'filename' => $filename,
'passkey' => $text
);
}
When I call this function, it prints on the webpage, e.g.

Can't write to /tmp/TsP1gTUNwAOyQ.png

However, that file clearly exists:

$ ll /tmp/TsP1gTUNwAOyQ.png
-rw-r--r-- www-data www-data 200 2005-11-09 /tmp/TsP1gTUNwAOyQ.png

How can is_writable() be wrong?

In related wierdness, I use this function like so:

$retval = createImage();
$filename = $retval['filename'];
$passkey = $retval['passkey'];
echo "<img src=\"$filename\" />";

But the image doesn't show up in the browser. When I look at the page
source, the statement is there and looks correct:

<img src="/tmp/c2GfviA4r4b47.png" />

and I can even view the image with xv and gimp, however, the image is simply
not on the webpage.

I strongly suspect that these two oddities are related, but I'm running out
of ideas. Anyone have any suggestions?

Thanks,
Pete

[Justin Koivisto]

Peter wrote:

Very perplexing. This function creates a png image of a random string (this
is to filter out blogging spam). It should be very straight forward.
function createImage( $text=0 )
{
$img_dir = '/tmp';

(snip!)

$filename = "$img_dir/" . randomString(12) . '.png';

if ( ! is_writable($filename) )
echo ("Can't write to $filename<br>");

ImagePNG( $image, $filename );
ImageDestroy( $image );

return array(
'filename' => $filename,
'passkey' => $text
);
}
When I call this function, it prints on the webpage, e.g.

Can't write to /tmp/TsP1gTUNwAOyQ.png

However, that file clearly exists:

$ ll /tmp/TsP1gTUNwAOyQ.png
-rw-r--r-- www-data www-data 200 2005-11-09 /tmp/TsP1gTUNwAOyQ.png

How can is_writable() be wrong?

In related wierdness, I use this function like so:

$retval = createImage();
$filename = $retval['filename'];
$passkey = $retval['passkey'];
echo "<img src=\"$filename\" />";

But the image doesn't show up in the browser. When I look at the page
source, the statement is there and looks correct:

<img src="/tmp/c2GfviA4r4b47.png" />

and I can even view the image with xv and gimp, however, the image is simply
not on the webpage.

I strongly suspect that these two oddities are related, but I'm running out
of ideas. Anyone have any suggestions?

The file isn't writable because it doesn't exist... you need to check
the directory...

<?php
if( (file_exists($filename)
&& is_writable($filename))
||
(file_exists(dirname($filename))
&& is_writable(dirname($filename)))
){
// can create or overwrite file
}else{
// cannot create or overwrite file
// directory may not exist, directory may
// now allow write permission, or the file
// exists and does not allow write permission
}
?>

--
Justin Koivisto, ZCE - ju****@koivi.com
http://koivi.com

[Peter Jay Salzman]

Justin Koivisto <ju****@koivi.com> wrote:

<?php
if( (file_exists($filename)
&& is_writable($filename))
||
(file_exists(dirname($filename))
&& is_writable(dirname($filename)))
){
// can create or overwrite file
}else{
// cannot create or overwrite file
// directory may not exist, directory may
// now allow write permission, or the file
// exists and does not allow write permission
}
?>

Doh! How embarrassing! But thanks! :)

Pete

[Chung Leong]

Should consider using tempnam() instead.

[Peter Jay Salzman]

Chung Leong <ch***********@hotmail.com> wrote:

Should consider using tempnam() instead.

Damn. This is why I *love* PHP. Great suggestion! Thank you!

I got my script working too. :)

Pete