Foolproofing pages that are not in a database

[La_Parka]

I have a page that uses index.php?id=X to retrieve information from a MySQL database.

If a user were somehow to manually enter a number for X that didn't have a corresponding row in the database, how can I make this page error-proof using PHP so that it will print an "Invalid Record Specified" message instead of displaying a page with blanks where all of the retrieved DB data is supposed to be?

[scoppc]

You can check whether the query was successful

//sql query here....
if ($query){
//display data...
}else{
//display error message
}

or else... check the number of rows the query returns... mysql_num_rows()
I am not sure whether this is effective, just give an idea.

[jcantrell]

I use the mysql_num_rows. Pretty much the same thing as scoppc said.

$num_rows =mysql_num_rows($query);
if ($num_rows > 0)
{
// Display data
}
else
{
// Display Error
}