<?php
    $zero = 0;
    $zeroStr = '0';
    $one  = 1;
    $oneStr = '1';
    if ($zero) {
        echo '$zero is not false';
    } else {
        echo '$zero is false';
    }
    echo PHP_EOL;
    if ($zeroStr) {
        echo '$zeroStr is not false';
    } else {
        echo '$zeroStr is false';
    }
    echo PHP_EOL;
    if ($one) {
        echo '$one is not false';
    } else {
        echo '$one is false';
    }
    echo PHP_EOL;
    if ($oneStr) {
        echo '$oneStr is not false';
    } else {
        echo '$oneStr is false';
    }
    echo PHP_EOL;
    if (empty($zeroStr) && empty($zero)) {
        echo 'failed1';
    } else {
        echo 'all1 is not empty';
    }
    echo PHP_EOL;
    if (empty($one) || empty($oneStr)) {
        echo 'failed2';
    } else {
        echo 'all2 is not empty';
    }
$zero is false
$zeroStr is false
$one is not false
$oneStr is not false
failed1
all2 is not empty