分配给布尔值的变量不会回显到 PHP 中的网页

Question

我有一些 PHP 代码应该检查是否分配了 $_GET 全局中的某个值。如果不是，它会自动输入一个预定值。如果存在，它会为变量分配一个默认值：<?phpif(!isset($spaceObjects)){  $spaceObjects = 0;} else{  $spaceObjects = $_GET['spaceObjects'] == true;}if(!isset($numOfStars)){  $numOfStars = 100;} else{  $numOfStars = intal($_GET['numOfStars']);}if(!isset($starTwinkles)){  $starTwinkles = 0;} else{  $starTwinkles = ($_GET ['starTwinkles'] == true);}if(!isset($numOfMeteorsMax)){  $numOfMeteorsMax = 8;} else{  $numOfMeteorsMax = intval($_GET['numOfMeteorsMax']);}if(!isset($twinklePausing)){  $twinklePausing = 1;} else{  $twinklePausing = ($_GET['twinklePausing'] == true);}if(!isset($nightCycle)){  $nightCycle = 0;} else{  $nightCycle = ($_GET['nightCycle'] == true);}if(!isset($music)){  $music = 1;} else{  $music = ($_GET['musicEnabled'] == true);}if(!isset($nightSounds)){  $nightSounds = 0;} else{  $nightSounds = ($_GET['nightSounds'] == true);}if(!isset($nightSoundsVol)){  $nightSoundsVol = 0.1;} else{  $nightSoundsVol = intval($GET['nightSoundsVol']);}?>let controlVariables = {  spaceObjects: <?php echo $spaceObjects;?>,  numOfStars: <?php echo $numOfStars;?>,  starTwinkles: <?php echo $starTwinkles;?>,  numOfMeteorsMax: <?php echo $numOfMeteorsMax;?>,  disableTwinklingWhileSpaceObjectGenerated: <?php echo $twinklePausing;?>,  nightCycle: <?php echo $nightCycle;?>,  music: <?php echo $music;?>,  nightSounds: <?php echo $nightSounds;?>,  nightSoundsVol: <?php echo $nightSoundsVol;?>};奇怪的是，PHP 在某些语句中什么也没给我echo，导致 JS 抛出语法错误。为什么不是打印true或falsePHP 在某些领域没有给我任何帮助？

Answer 1

尝试用条件替换 echo 以输出特定文本而不是变量本身。Echoed boolean 为真时输出 1，当变量为假时不输出任何内容。例如：

let controlVariables = {
    spaceObjects: <?php echo ($spaceObjects)? 'true' : 'false';?>,
...
}