Question

I have a page called Error.php. Variables are usually passed to it using the query string so that it will display the corresponding message to the error code I have assigned.

Example: Error.php?id=1

Here is the section of my page below:

<?php
if($_GET["id"] == "0")
{
  echo "Display certain information...";
}
elseif($_GET["id"] == "1")
{
  echo "Display certain information...";
}
elseif($_GET["id"] == "2")
{
  echo "Display certain information...";
}
elseif($_GET["id"] == "3")
{
  echo "Display certain information...";    
}
else
{
  echo "Display certain information...";
}
?>

All the information works fine, but the only problem is, if there is no query string (leaving it as just “Error.php”), it displays errors saying “Undefined index: id in…..”. Is there a way to make Error.php unaccessible unless there is a query string? I’m sorry if my code grammer is incorrect, I’m very new to PHP. Thank you.

Answer 1

Use array_key_exists() to check and see if it’s there:

<?php

if(array_key_exists("id", $_GET)) 
{
    if($_GET["id"] == "0")
    {
      echo "Display certain information...";
    }
    elseif($_GET["id"] == "1")
    {
      echo "Display certain information...";
    }
    elseif($_GET["id"] == "2")
    {
      echo "Display certain information...";
    }
    elseif($_GET["id"] == "3")
    {
      echo "Display certain information...";    
    }
    else
    {
      echo "Display certain information...";
    }
}
else
{
  // no query id specified, maybe redirect via header() somewhere else?
}

?>