dqqvravff05370501 2016-07-01 20:14
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如何使用javascript从PHP if语句更改iframe的源代码

Based on the result of a PHP if statement, I want to change the source attribute of an iframe.

I have the following:

<?PHP
     if {...}
     else {
          echo "<script>";
          echo "document.getElementById('video-embed').setAttribute('src', 'https://www.youtube.com/embed/dQw4w9WgXcQ');";
          echo "</script>";
     }
?>

<!DOCTYPE html>
     <body>
        <div class="wrapper">
          <iframe id="video-embed" src="...some other youtube video"></iframe>
        </div>
     </body>
</html>

I know that executing valid JavaScript from the if statement is at least feasible, as I've succesfully tested JS alerts. Everything I've seen online has seemed to indicate that the syntax in question for the line "document.getElem..." is valid. Any help would be appreciated.

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  • donglian1384 2016-07-01 21:14
    关注

    You have the Javascript before the HTML that creates the element that it's trying to modify, so getElementById() isn't finding the element. Move the PHP code that adds the JS to the end of the HTML, so that the ID will be found. Or put the Javascript in the window's load handler. 

    <?PHP
     if {...}
     else {
          echo "<script>";
          echo "window.addEventListener('load', function() {";
          echo "document.getElementById('video-embed').setAttribute('src', 'https://www.youtube.com/embed/dQw4w9WgXcQ');";
          echo "});";
          echo "</script>";
     }
?>
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