test1.php

<?php
$a = 5;
function test() {
    static $a = 0;
    return ++$a;
}

echo test();
echo test();
echo test();
exit;

结果：123

test2.php

<?php
$a = 5;
function test() {
    $a = 0;
    return ++$a;
}

echo test();
echo test();
echo test();
exit;

结果：111