<?php
    $num1 = 15;
    $num2 = 15.5;
    echo $num1+$num2;
    echo "<br>";
?>

<?php
    $x = 5;//Global
    function myTest(){
        $y = 10;//Local
        echo "x：$x";
        echo "<br>";
        echo "y：$y";
        echo "<br>";
    }
    myTest();
    echo "<hr>";
    echo "x：$x";
    echo "<br>";
    echo "y：$y";
?>

<?php
    $c = 10;
    $d = 20;
    function test(){
        global $c, $d, $f;
        $f = $c + $d;
    }
    test();
    echo "$f";
?>

<?php
    $x = 5;
    $y = 15;
    function test4(){
        $GLOBALS[‘y‘] = $GLOBALS[‘y‘] + $GLOBALS[‘x‘];
    }
    test4();
    echo "$y";
?>

<?php
    function myTest() {
          static $x=0;
          echo $x;
          $x++;
    }
    myTest();
    myTest();
    myTest();
?>