我在PHP中有一个变量，并且我的JavaScript代码中需要它的值.如何将变量从PHP转换为JavaScript？
我有这样的代码:
<?php
$val = $myService->getValue(); // Makes an API and database call
在同一页上，我有JavaScript代码，需要将$val变量的值作为参数传递:
<script>
myPlugin.start($val); // I tried this, but it didn't work
<?php myPlugin.start($val); ?> // This didn't work either
myPlugin.start(<?=$val?>); // This works sometimes, but sometimes it fails
</script>
实际上有几种方法可以做到这一点.有些需要比其他人更多的开销，有些被认为比其他人更好.
没有特定顺序:
在本文中，我们将研究上述每种方法，并了解每种方法的优缺点，以及如何实现它们.
这种方法被认为是最好的，因为your server side and client side scripts are completely separate.
使用Ajax，您需要两个页面，一个是PHP生成输出的地方，另一个是JavaScript获取输出的地方:
/* Do some operation here, like talk to the database, the file-session
* The world beyond, limbo, the city of shimmers, and Canada.
*
* AJAX generally uses strings, but you can output JSON, HTML and XML as well.
* It all depends on the Content-type header that you send with your AJAX
* request. */
echo json_encode(42); // In the end, you need to echo the result.
// All data should be json_encode()d.
// You can json_encode() any value in PHP, arrays, strings,
//even objects.
<!-- snip -->
<script>
function reqListener () {
console.log(this.responseText);
}
var oReq = new XMLHttpRequest(); // New request object
oReq.onload = function() {
// This is where you handle what to do with the response.
// The actual data is found on this.responseText
alert(this.responseText); // Will alert: 42
};
oReq.open("get", "获取数据.php", true);
// ^ Don't block the rest of the execution.
// Don't wait until the request finishes to
// continue.
oReq.send();
</script>
<!-- snip -->
当文件加载完成时，上述两个文件的组合将向42发出alert .
这种方法不如AJAX好，但它仍然有它的优点.从某种意义上说，PHP和JavaScript之间仍然有relatively个分隔，JavaScript中没有直接的PHP.
<input type=hidden>来存储信息，因为从inputNode.value中获取信息更容易，但这样做意味着你的HTML中有一个无意义的元素.HTML有<meta>个元素来表示文档的数据，HTML5为数据引入了data-*个属性，这些属性专门用于使用JavaScript阅读，可以与特定元素关联.这样做的目的是创建某种元素，这些元素不会显示给用户，但对JavaScript是可见的.
<!-- snip -->
<div id="dom-target" style="display: none;">
<?php
$output = "42"; // Again, do some operation, get the output.
echo htmlspecialchars($output); /* You have to escape because the result
will not be valid HTML otherwise. */
?>
</div>
<script>
var div = document.getElementById("dom-target");
var myData = div.textContent;
</script>
<!-- snip -->
这可能是最容易理解的.
实施相对简单:
<!-- snip -->
<script>
var data = <?php echo json_encode("42", JSON_HEX_TAG); ?>; // Don't forget the extra semicolon!
</script>
<!-- snip -->
祝你好运！