[Adrian Schneider]

The condition between the two quotes is parsed as a boolean expression.

Originally Posted by PHP Manual

When converting to boolean, the following values are considered FALSE:

• the boolean FALSE itself
• the integer 0 (zero)
• the float 0.0 (zero)
• the empty string, and the string "0"
• an array with zero elements
• an object with zero member variables (PHP 4 only)
• the special type NULL (including unset variables)
• SimpleXML objects created from empty tags

Every other value is considered TRUE (including any resource).

Usually in templates, you'd check the value of options or user settings. Unless you really understand the above, it's best to use comparisons to avoid mix ups.

<if condition="$variable == 'Yes'"> 
<if condition="$variable > 10">
<if condition="$vbulletin->options['something_enabled']">

etc.