为什么我的JS的位置改变了我的HTML代码?

Rob*_*ain 2 html javascript php

我不知道JS的位置可能会改变我的html页面的结果,直到今天.我希望图像src在两个不同的URL"点击"之间切换.为什么这个第一个代码的工作方式与我想要的一样,但第二个代码却没有?第二个代码的源html为var not_a_bad_word生成一个空字符串.

第一个代码:

<!DOCTYPE HTML>
<html>
    <head>
        <meta charset="UTF-8">
        <title>'Murica!'</title>
    </head>
    <body>
        <?php
        $dbhost = 'databasePlace';
        $dbname = 'mine';
        $dbuser = 'me';
        $dbpass = '*****';

        $link = mysqli_connect($dbhost, $dbuser, $dbpass, $dbname);
        mysqli_select_db($link, $dbname);
        $name = $_GET["fname"];

        $query = sprintf(
            "SELECT image_url, Type
             FROM Pokemon c
             WHERE c.name = '%s'", 
             mysqli_real_escape_string($link, $name));

        $result = mysqli_fetch_assoc(mysqli_query($link, $query));

        echo '<img id="pokemon_card" onclick="changeImage()" height="450" 
                  width="330" src="' . $result['image_url'] . '"/>';

        mysqli_close($link);
        ?>
        <script>
            function changeImage() {
                element = document.getElementById('pokemon_card');
                var not_a_bad_word = "<?php echo $result['image_url']; ?>";

                if (element.src == "http://dmisasi.files.wordpress.com/2010/12/david-pokemon-card-back.jpg") {
                    element.src = not_a_bad_word;
                }
                else {
                    element.src="http://dmisasi.files.wordpress.com/2010/12/david-pokemon-card-back.jpg";
                }
            }
        </script>
    </body>
</html>
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第二个代码:

<!DOCTYPE HTML>
<html>
    <head>
        <meta charset="UTF-8">
        <title>'Murica!</title>
        <script>
            function changeImage() {
                element = document.getElementById('pokemon_card');
                var not_a_bad_word = "<?php echo $result['image_url']; ?>";

                if (element.src == "http://dmisasi.files.wordpress.com/2010/12/david-pokemon-card-back.jpg") {
                    element.src = not_a_bad_word;
                }
                else {
                    element.src="http://dmisasi.files.wordpress.com/2010/12/david-pokemon-card-back.jpg";
                }
            }
        </script>
    </head>
    <body>
        <?php
        $dbhost = 'databasePlace';
        $dbname = 'mine';
        $dbuser = 'me';
        $dbpass = '*****';

        $link = mysqli_connect($dbhost, $dbuser, $dbpass, $dbname);
        mysqli_select_db($link, $dbname);
        $name = $_GET["fname"];

        $query = sprintf(
            "SELECT image_url, Type
             FROM Pokemon c
             WHERE c.name = '%s'", 
             mysqli_real_escape_string($link, $name));

        $result = mysqli_fetch_assoc(mysqli_query($link, $query));

        echo '<img id="pokemon_card" onclick="changeImage()" height="450" 
                  width="330" src="' . $result['image_url'] . '"/>';

        mysqli_close($link);
        ?>
    </body>
</html>
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Jan*_*nen 5

在第一个示例中,创建变量的PHP代码在变量echo 之前$result['image_url']运行.

如果你看第二个产生空白的例子,$result['image_url']实际上只是它被回应定义.