Details about how to use the ThinkPHP template to determine the output Present tag

The present label of the ThinkPHP template is usedDetermine whether the template variable has been assigned a value.

The present tag of the ThinkPHP template engine is used to determine whether the template variable has been assigned a value,Its function is equivalent to the isset () function behavior in PHP.The format is as follows:

<Present name = "variable name"> content to be output </present>

Examples:

<Present name = "username"> {$ username} Hello! </Present>

This example is equivalent:

If (isset ($ username) {echo "$ username hello! ";}

In addition, the notpresent label can be used to judge whether no value is assigned. The usage is as follows:

<Notpresent name = "username"> the username does not exist and is not logged on </notpresent>

You can also merge the preceding two labels:

<Present name = "username"> {$ username} Hello! <Else/> the username does not exist and is not logged on </present>