如何在PHP中将数组声明为全局？

这是我的代码..

Index.php page...

<?php
    $arr = array();

    $ourFileName = "saved_data.txt";
    $ourFileHandle = fopen($ourFileName,'w') or die("can't open file");
    fwrite($ourFileHandle,"");

?>

Ajax页面…..

<?php
    $name_full = $_GET['name_full'];
    $arr = $_GET['$arr'];

    array_push($arr,$name_full);
    /*------------To create a file-----------------*/
    $ourFileName = "saved_data.txt";
    $ourFileHandle = fopen($ourFileName,'w') or die("can't open file");
    /*---------To save data in the file------------*/
    foreach($arr as $key => $value)
    {
        fwrite($ourFileHandle,$value);
    }
    fwrite($ourFileHandle,',');
    fclose($ourFileHandle);
    echo $name_full;
?>

还有什么办法让这个数组全局化……