php href file reference confusion in header section

StackOverflow https://stackoverflow.com/questions/23230154

  •  07-07-2023
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Question

I am doing something very simple, and would like some insight as to why some file path references work and others don't. My test code is as follows:

<?php
$menu1 = 'c:/xampp/htdocs/data/sc01/includes/menu.php';
$menu2 = 'http://localhost/data/sc01/includes/menu.php';
$test1 = 'http://localhost/data/sc01/css/style.css';
$test2 = 'c:/xampp/htdocs/data/sc01/css/style.css';
$test3 = 'css/style.css';
echo $test1; echo "<br>";  
echo $test2; echo "<br>"; 
echo $test3; echo "<br>"; 
?>
<!doctype html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <link rel="stylesheet" type="text/css" href="<?php echo $test2; ?>">
    <link rel="stylesheet" href="css/font-awesome.min.css">
    <title>Index</title>
</head>
<body>  
<div id="container">
    <?php include "$menu1"; ?>
    <h1>Welcome to our site!</h1>
    <p>This is a test coment</p>
</div>
</body>

<div class="footer-container">
    <?php include "c:/xampp/htdocs/data/sc01/includes/footer.php"; ?>
</div>
</html>

My questions:

  1. In the header section to reference the css file: $test1 works, $test2 does NOT work, $test3 works. In the echo statements to check these, all the paths seem to verify correctly. WHY IS THIS? - I would have thought all of these should work?
  2. In the container section to access the navigation menus, $menu1 works, $menu2 does not - gives PHP errors. WHY IS THIS? - I would have thought all of these should work?
  3. In the include menu code, ?php include "$menu1"; ?, double quotes work. But single quotes '$menu1' does not work, but I thought single or double quotes should yield the same results. WHY IS THIS?

Thanks in advance!

Was it helpful?

Solution

None of the strings beginning with c: are valid URLs, so you can't use them in href or src attributes in HTML. You can use them in PHP include lines because those are processed by the server, and it allows the argument to be local filenames.

<?php include '$menu1' ?>

doesn't work because PHP only expands variables inside doublequoted strings, not inside singlequoted strings. It's just like the difference between:

echo "$menu1";

and

echo '$menu1';

The first will echo the value of the variable, the second will echo $menu1 literally.

OTHER TIPS

Including via http:// vs via file system path are two significantly different things – the first one will only get you the output of the script¹, whereas the second one includes the code of the file, and then runs it within the scope the main script afterwards.

In the include menu code, <?php include "$menu1"; ?>, double quotes work. But single quotes '$menu1' does not work, but I thought single or double quotes should yield the same results. WHY IS THIS?

Because you “think” instead of reading up on the very basics of the syntax. So go fix that now: http://www.php.net/manual/en/language.types.string.php

¹ Assuming of course, that requesting the file via HTTP means that it is put through the PHP interpreter by the web server first, but that is usually the case.

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