WordPress page content randomly inserting inside of shortcode - php

Question

I am writing a plugin where you put in a shortcode in a page and it displays a table of data.
However, the page content prior to the shortcode is being inserted randomly into the middle of the table. When I refresh the page the content typed above the shortcode randomly moves within the table produced by the shortcode.
Content under the shortcode does not appear within the shortcode return.
Does anyone have any idea why this might be happening. This is super strange.
------------------ wordpress page edit ---------------
Here is some content.
Here is another paragraph.
[view_contributions]
End of page content.
------------------end of wordpress page edit ----------------------------
It then produces
------ displays --------
[Shortcode data table with "Here is some content. Here is another paragraph." randomly inserted into a cell somewhere. Then more data table]
End of page content.
-------- end of display -----
This is so odd. It's as if shortcode is rendering first but then WordPress injects the page content into whatever the shortcode is rendering. Any ideas what could cause this?
EDIT: Added entirety of code in case something really strange is happening...
function soco_view_contributions_shortcode() {
$view_contributions = Soco_Contributions::soco_display_contributions();
return $view_contributions;
}
add_shortcode( 'view_contributions', 'soco_view_contributions_shortcode');
public function soco_display_contributions() {
$contribution_results = Soco_Contributions::soco_get_contributions_view();
ob_start;
?>
<div name="div-output-container">
<form name="frm-search-contributions">
<table width="100%" border="0">
<tbody>
<tr>
<th scope="col">Start Date</th>
<th scope="col">End Date</th>
<th scope="col">Minimum</th>
<th scope="col">Maximum</th>
<th scope="col">Name</th>
<th scope="col">Event</th>
</tr>
<tr>
<td><input type="date" name="start-date"></td>
<td><input name="end-date" type="date" ></td>
<td><input type="number" name="low-number"></td>
<td><input type="number" name="high-number"></td>
<td><text name="txt-auto-name"> </textarea></td>
<td><select> </select></td>
</tr>
</tbody>
</table>
<input type="submit">
<input type="reset">
</form>
<table width="100%" border="0">
<tbody>
<tr>
<th scope="col">Date</th>
<th scope="col">Amount</th>
<th scope="col">Cycle</th>
<th scope="col">Name</th>
<th scope="col">Event</th>
</tr>
<?php foreach ($contribution_results as $cr) { ?>
<tr>
<td><?php echo $cr->contribution_date ?></td>
<td><?php echo $cr->amount ?></td>
<td><?php echo $cr->cycle_amount ?></td>
<td><?php echo $cr->last_name.', '.$cr->first_name ?></td>
<td> </td>
</tr>
<?php } ?>
</tbody>
</table>
<button name="btnDownload" id="btnDownload" title="Click this button to download the above dataset." >Download CSV File</button>
</div>
<?php
$contribution_output = ob_get_clean();
return $contribution_output;
}

Answer 1

It seems that you are attempting to return an output buffer as string. When ob_start() is called, all output is suppressed until ob_end(), ob_end_flush() or ob_end_clean() is called so logically, you can't return it. Simply call them within the function itself and return the contents of the output buffer (ob_get_contents()) as a string:
add_shortcode('view_contributions','soco_view_contributions_shortcode');
function soco_view_contributions_shortcode( ) {
ob_start();
?>
<h1>Shortcode Output</h1>
<p><?php echo "Some other output" ?></p>
<?
return ob_end_clean();
}
Why PHP doesn't throw a fatal error when attempting to return an entire buffer from a function surprises me.

Answer 2

The problem turned out to be mixing ECHO and RETURN in the output buffer. To fix this I turned the whole thing into a concatenated string to output instead.
The echos that are in the foreach loop I think were messing up the output buffer. So I removed ob_start all together and will just output a final HTML string.
Not a great solution but at least it is working now and not producing random results. If anyone has suggestions or examples on how to mix ob_start with php logic inside of it that would be great. It seems weird to me that ob_start() has issues with this.
$contribution_output = '<div name="div-output-container">
<form name="frm-search-contributions">
<table width="100%" border="0">
<tbody>
<tr>
<th scope="col">Start Date</th>
<th scope="col">End Date</th>
<th scope="col">Minimum</th>
<th scope="col">Maximum</th>
<th scope="col">Name</th>
<th scope="col">Event</th>
</tr>
<tr>
<td><input type="date" name="start-date"></td>
<td><input name="end-date" type="date" ></td>
<td><input type="number" name="min-amount"></td>
<td><input type="number" name="max-amount"></td>
<td>
<input type="text" name="donor_name">
<input type="hidden" name="hdn-donor-id" value="">
</td>
<td><select> </select></td>
</tr>
</tbody>
</table>
<input type="submit">
<input type="reset">
</form>
<div name="contribution-results-container" >
<table width="100%" border="0">
<tbody>
<tr>
<th scope="col">Date</th>
<th scope="col">Amount</th>
<th scope="col">Cycle</th>
<th scope="col">Name</th>
<th scope="col">Event</th>
</tr>';
foreach ($contribution_results as $cr) {
$contribution_output .= '
<tr>
<td>'.$cr->contribution_date.'</td>
<td>'.$cr->amount.'</td>
<td>'.$cr->cycle_amount.'</td>
<td>'.$cr->last_name.', '.$cr->first_name.'</td>
<td> </td>
</tr>';
}
$contribution_output .= '</tbody>
</table>
<button name="btnDownload" id="btnDownload" title="Click this button to download the above dataset." >Download CSV File</button>
</div>
</div>';