include_once in php

The include_once()statement include and evaluates the specified file during of execution of the script.This is a behavior similar to the include() function with the only difference being that it code from a file has already been included.It will not be included again.

Syntax
include "function name";
Example
vars.php

<?php $color='red'; $fruit='apple'; echo $fruit."color is".$color" ?>

test.php

<?php echo "a $color $fruit" // include 'vars.php include_once'vars.php' echo "a $color $fruit" ?>

Output:

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