问为什么我的本地PHP函数不能看到$test变量，以及如何获得它的值？

EN

function NowHereDoc(  &$_vars_, &$_array_ ) { // a by-ref array of variables and their values from the caller's scope.
                                              //
                                              // a by-ref array specifying the web-content as a string that
                                              // contains one or more PHP variables in the ${...} format who's
                                              // values are to be substituted for the variable name.
                                              //
                                              //  & By-Ref prefix minimizes data movement when calling this function.
                                              //

    $_l_ = count( $_array_ );
    $_s_ = $_array_[ $_l_ - 1 ]; // Get the last element's string value.

    // Find each ${...} and substitute the variable's value ...

    $_i1_ = 0;
    while( ( $_i1_ = strpos( $_s_, '${', $_i1_ ) ) !== FALSE ) { // Get index of start of a variable name specified
                                                                 //  by ${...} or FALSE when there aren't any {more},
                                                                 // then stop looping.

        $_i2_  = strpos( $_s_, '}', $_i1_ );                     // Get index of end of the ${...} just found.
        $_l_   = $_i2_ - $_i1_ + 1;                              // Get length of ${...}.
        $_var_ = substr( $_s_, $_i1_, $_l_ );                    // Get the variable's name as a string.
        $_v_   = str_replace( [ '$', '{', '}' ], '', $_var_ );   // Remove { and } from the variable name.
        $_val_ = $_vars_[ $_v_ ];                                // Get the value of the specified variable.

        // Substitute the variable's value into the original string, $_s_

        // $_s_ = substr_replace( $_s_, $_val_, $_i1_, $_l_ );  // Replace the single occurance of the variable
                                                                 // with its value. This could to replace occurances
                                                                 // not with in comments, not yet implemented in
                                                                 // function.

        $_s_   = str_replace( $_var_, $_val_, $_s_ );            // Replace all occurances of the variable with its
                                                                 // value.

    } // End of while( ( $_i1_ = strpos( $_s_, '${', $_i1_ ) ) !== FALSE ) ...

    $_array_[ $_l_ - 1 ] = $_s_;                                 // Set the last element's string value to the
                                                                 // updated string in $_s_.

}

// No variable substitutions.
$strMAINs[] = <<<'MAIN'
<!-- 
=======================================================================
=======================================================================                     
=
= ${test1} ${test2} // ${test1} ${test2} should be substituted with hi there
=          
=======================================================================          
=======================================================================
-->
MAIN;

$test1 = 'hi';
$test2 = 'there';

$vars = get_defined_vars();
NowHereDoc( $vars, $strMAINs );

// global scope
$test = 'my string';

function myFunction() {
    global $test;
}

function myOuterFn() {
    $test = 'my string';
    $myInnerFn = function() use ($test) {
        echo $test;
    };
}