Can you tell me your opinion of this, and possibly see if you can recreate it? There are TWO scenarios:
SCENARIO 1 (works as intended)...
The $post->post_content variable contains this (with a VALID image src):
(string) "before [hw] <img src="/path/to/valid_image.gif" /> after"
This code placed at the top of the theme header.php...
1: echo test_out();
2:
3: function test_out() {
4: global $post;
5: error_log( 'stage_1' );
6: $str = $post->post_content;
7: error_log( 'stage_2' );
8: var_dump( isset( $str ) );
9: error_log( 'stage_3' );
10: $str = test_core_wp( 'test_shortcode', $str );
11: error_log( 'stage_4' );
12:
13: return $str;
14: }
15:
16: function test_shortcode( $content ) {
17: return str_replace( '[hw]', 'Hello World!', $content );
18: }
19:
20: function test_core_wp( $function, $a = NULL ) {
21: $wrap = array ( 'test_shortcode' => 'test_shortcode' );
22:
23: if ( isset( $a ) ) $args[] = $a;
24:
25: return call_user_func_array( $wrap[ $function ], $args );
26: }
Outputs this (correctly)...
bool(true)
before Hello World! <img src="/path/to/valid_image.gif" /> after
With this in the PHP log (correctly)...
[22-Jul-2009 11:49:36] stage_1
[22-Jul-2009 11:49:36] stage_2
[22-Jul-2009 11:49:36] stage_3
[22-Jul-2009 11:49:36] stage_4
SCENARIO 2 (where the problem occurs)...
The $post->post_content variable now contains: (with an INVALID image src):
(string) "before [hw] <img src="/path/to/broken_image.gif" /> after"
Outputs this (STILL correctly)...
bool(true)
before Hello World! <img src="/path/to/broken_image.gif" /> after
With this in the PHP log (THIS IS THE PROBLEM)...
[22-Jul-2009 11:56:11] stage_1
[22-Jul-2009 11:56:11] stage_2
[22-Jul-2009 11:56:11] stage_3
[22-Jul-2009 11:56:11] stage_4
[22-Jul-2009 11:56:11] stage_1
[22-Jul-2009 11:56:11] stage_2
[22-Jul-2009 11:56:11] stage_3
[22-Jul-2009 11:56:11] PHP Warning: Missing argument 1 for test_shortcode() in
/path/to/header.php on line 16
[22-Jul-2009 11:56:11] stage_4
The test-out() function seems to be running itself TWICE, but only when $post->post_content contains a broken image.
FYI, with Firefox you can reload the web page source by hitting CTRL-R. When reloading the source, no problems. However, when reloading the web page in the browser tab (or ANY browser), I get the warning shown above.
I have confirmed the oddity only occurs when there is a broken img src in the variable $post->post_content (or any of the $post variables, for you WordPress gurus).
Any chance you can reproduce this and tell me what you think? I'm new to PHP, but I'm pretty sure something is going on that is way beyond my knowledge. :)
EDIT:
I was about to start checking my local dev environment, but a friend wrote me:
After looking at your post, I think I may have an idea what's going on.
I had assumed that the warning message you were talking about was being displayed in the browser when you loaded the page in question, but your post indicates that you're seeing the warning message in the PHP log instead. Is it only appearing in the PHP log? YES
If that's so, then consider this explanation....
In the case where you the post body contains an tag to a valid image, then your code is being run once to generate the page as expected. The browser sees the rendered page and then attempts to load the image. The server finds the image and dishes it up directly - no surprises here.
In the case where the post body contains an tag to an invalid image, then your code is being run once to generate the page, just as before. Then the browser makes a separate HTTP connection to attempt to load the image. Normally, it would just trigger a 404 error and the browser would display a broken image, end of story. However, if the broken image URL is to something under your Wordpress installation, then Wordpress overrides the default web server 404 behavior and dishes up a fancy "404 Not Found" page instead of the web server's default 404 page. Here's the kicker -- Wordpress's fancy 404 page includes the same header and footer as all the other pages it displays. So if you have this code at the top of your header, it'll get called again by the 404 page that the web server sends in response to the missing image your browser requested from it.
You never actually see the 404 page in this case, because it's being generated in response to an request, not a page request, so the browser just treats the response as a bad image and shows the broken image icon, but it is actually being generated and sent.
Compare this (a valid image URL under a Wordpress installation):
http://www.example.com/foo.jpg
to this (an invalid image URL under a Wordpress installation):
http://www.example.com/foo.jpg
Note the custom 404 page including header that gets returned...?
And... in the context of the 404 page, the $post object doesn't exist, so $post->post_content obviously isn't a string.
I had assumed that the warning message was being displayed in the browser on the original page load, which is why I didn't really consider this situation, but if it's just being output to your PHP log, then it makes perfect sense.
And if that is the case, then you can either ignore the warning as it really makes no difference, or you can test for that situation in your code (like the isset workaround you mentioned before).
Any other thoughts, let me know, but that seems to fit with what I know about it so far.
