Why would apply_filters return a non-empty string, when the value returned is empty?

Question

Been breaking my keyboard over this. Did a proper install, uploaded the database to a fresh MySQL and been working on using child themes properly. But there is something plaguing me I can not figure out.

On my new install (ver2.whowhatwhy.com) I intentionally left some of my widgets blank. I would expect, when reading the default-widgets.php file in wp-includes that there would be no title element showing on that widget.

Instead, the title widget is showing because, for some reason, the value being passed by apply_filters is a space, rather than a blank value when the $instance['title'] is blank.

$title = apply_filters( 'widget_title', empty( $instance['title'] ) ? '' : $instance['title'], $instance, $this->id_base );

Has anyone seen this before? The problem I have is that the original installation has no problem with this call (returns a blank value).

If you go to the site, you can see the vardumps of the different elements of the code:

function widget( $args, $instance ) {
        extract($args);
        $title = apply_filters( 'widget_title', empty( $instance['title'] ) ? '' : $instance['title'], $instance, $this->id_base );
        $text = apply_filters( 'widget_text', empty( $instance['text'] ) ? '' : $instance['text'], $instance );
        echo $before_widget;
        if ( !empty( $title ) ) { echo $before_title . '[' . $title . '] ' . $after_title; } ?>
            <div class="textwidget"><?php echo !empty( $instance['filter'] ) ? wpautop( $text ) : $text; ?></div>
        <?php
        echo $after_widget;
    }

I also removed all of the widgets and then replaced the one widget on the page. This is what is in the database:

@Otto - I also looked in the database and eliminated all of the other widgets. And here is what I found:

a:2:{i:916707761;a:3:{s:5:"title";s:0:"";s:4:"text";s:1333:"<table width="297" bgcolor="#000000">
  <tr>
    <td width="297" bordercolor="0"><!-- BEGIN: Constant Contact Stylish Email Newsletter Form -->
<div align="center">
<div style="width:267px; background-color: #000000;">
<form name="ccoptin" action="http://visitor.r20.constantcontact.com/d.jsp" target="_blank" method="post" style="margin-bottom:3;">
  <p><span class="style1" style="font-family: Arial, Helvetica, sans-serif"><font style="font-family:Arial; font-size:18px; color:#666666;"><span class="style4">Do you need the truth?</span><br>
    </font><span style="font-size: 12px"><font style="font-family:Arial; font-size:14px; color:#FF0000;">Sign up for our weekly email updates and stay informed. </font></span></span></p>
  <p>
        <input type="text" name="ea" size="22" value="" style="font-family:Verdana,Geneva,Arial,Helvetica,sans-serif; font-size:14px; border:1px solid #999999;">
        <input type="submit" name="go" value="JOIN" class="submit"  style="font-family:Verdana,Arial,Helvetica,sans-serif; font-size:10px;">
        <input type="hidden" name="llr" value="">
        <input type="hidden" name="m" value="">
        <input type="hidden" name="p" value="">
    </p>
</form>
</div>
</div>
</td>
  </tr>
</table>
<div style="margin-bottom: 2px;">&nbsp;</div>
";s:6:"filter";b:0;}s:12:"_multiwidget";i:1;}

Note where the a:3 is, you can see that the title value is an empty string with no length.

So, why would apply_filters return a non-empty value?

Answer 1

The problem is in the theme you're using. This has been reported before:

https://core.trac.wordpress.org/ticket/21430

Seems that Elegant Themes don't like their widgets to not have titles. So they have a function called "et_widget_force_title" which changes blank titles into titles with a single space.

In case of doubt, always try disabling plugins and switching to the default theme. You never can tell what other plugins or themes are doing.