php $_GET and undefined index

A new problem has arisen for me as I tried to run my script on a different PHP Server.

ON my old server the following code appears to work fine - even when no s parameter is declared.

<?php
 if ($_GET['s'] == 'jwshxnsyllabus')
echo "<body onload=\"loadSyllabi('syllabus', '../syllabi/jwshxnporsyllabus.xml',         '../bibliographies/jwshxnbibliography_')\">";
if ($_GET['s'] == 'aquinas')
echo "<body onload=\"loadSyllabi('syllabus', '../syllabi/AquinasSyllabus.xml')\">"; 
 if ($_GET['s'] == 'POP2')
echo "<body onload=\"loadSyllabi('POP2')\">";
elseif ($_GET['s'] == null)
echo "<body>"
?>

But now, on a my local server on my local machine (XAMPP - Apache) I get the following error when no value for s is defined.

Notice: Undefined index: s in C:\xampp\htdocs\teaching\index.php on line 43
Notice: Undefined index: s in C:\xampp\htdocs\teaching\index.php on line 45
Notice: Undefined index: s in C:\xampp\htdocs\teaching\index.php on line 47
Notice: Undefined index: s in C:\xampp\htdocs\teaching\index.php on line 49

What I want to happen for the script to call certain javascript functions if a value is declared for s, but if nothing is declared i would like the page to load normally.

Can you help me?

Solution 1:

Error reporting will have not included notices on the previous server which is why you haven't seen the errors.

You should be checking whether the index s actually exists in the $_GET array before attempting to use it.

Something like this would be suffice:

if (isset($_GET['s'])) {
    if ($_GET['s'] == 'jwshxnsyllabus')
        echo "<body onload=\"loadSyllabi('syllabus', '../syllabi/jwshxnporsyllabus.xml',         '../bibliographies/jwshxnbibliography_')\">";
    else if ($_GET['s'] == 'aquinas')
        echo "<body onload=\"loadSyllabi('syllabus', '../syllabi/AquinasSyllabus.xml')\">"; 
    else if ($_GET['s'] == 'POP2')
        echo "<body onload=\"loadSyllabi('POP2')\">";
} else {
    echo "<body>";
}

It may be beneficial (if you plan on adding more cases) to use a switch statement to make your code more readable.

switch ((isset($_GET['s']) ? $_GET['s'] : '')) {
    case 'jwshxnsyllabus':
        echo "<body onload=\"loadSyllabi('syllabus', '../syllabi/jwshxnporsyllabus.xml',         '../bibliographies/jwshxnbibliography_')\">";
        break;
    case 'aquinas':
        echo "<body onload=\"loadSyllabi('syllabus', '../syllabi/AquinasSyllabus.xml')\">";
        break;
    case 'POP2':
        echo "<body onload=\"loadSyllabi('POP2')\">";
        break;
    default:
        echo "<body>";
        break;
}

EDIT: BTW, the first set of code I wrote mimics what yours is meant to do in it's entirety. Is the expected outcome of an unexpected value in ?s= meant to output no <body> tag or was this an oversight? Note that the switch will fix this by always defaulting to <body>.

Solution 2:

Get into the habit of checking if a variable is available with isset, e.g.

if (isset($_GET['s']))
{
     //do stuff that requires 's'
}
else
{
     //do stuff that doesn't need 's'
}

You could disable notice reporting, but dealing them is good hygiene, and can allow you to spot problems you might otherwise miss.

php $_GET and undefined index

Solution 1:

Solution 2:

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