The "show whitespace characters" setting controls this for most editors I've used, such as the Java editor. Perhaps there is a PHP-specific editor setting that is separate from the general Text Editors one; did you look under the PHP section of Preferences?
As you can see at the dialog linked from Preferences->General->Editors->Text Editors->Show whitespace characters, Eclipse uses "≫", "¶" or so as whitespaces.
Your screenshot is different from Eclipse.
I'm guessing you must have a third party plugin such as JStyle for example. Have a look at Preferences->General->JStyle if it is there.