how to catch error code in PHP

Question

i want to add records to table 'pool' with attribute ID and empName from database employees

theform.html

<FORM NAME ='form2' METHOD ='POST' ACTION ='result.php' enctype="multipart/form-data">
<B>Board Write</B> <BR>

<INPUT TYPE = Text Name = empID value = 'write ID here'>
<INPUT TYPE = Text Name = empName  VALUE = 'write name here'><P>
<INPUT TYPE = 'Submit' Name = Submit2  VALUE = 'Post'>

</FORM>

result.php

<?PHP

      $ID = $_POST['empID'];
      $NAME = "'" . $_POST['empName'] . "'";

       $server = "127.0.0.1"; //connect to server
       $user_name = "root";   
       $password = "";

       $database = "employees";


    $db_handle = mysql_connect($server, $user_name, $password);
    $db_found = mysql_select_db($database, $db_handle);


if($db_found){// there is a database

$tableSQL = "INSERT INTO pool(ID, empName) VALUES " . "(" . $ID . "," . $NAME . ")";


$result = mysql_query($tableSQL);

    if($result){
            print "success!";
    }
    else{
            print "fail!";
        }


}

   mysql_close($db_handle);  //close the connection;



?>

in the database, ID is unique and also an INT datatype, i want to catch the error code where the user inputs an ID value that already existing in the database. how do we do this?

First of all you should prevent getting any errors, e.g. by [protecting your script against SQL injection](http://stackoverflow.com/questions/60174/best-way-to-stop-sql-injection-in-php). Then you should [take a look into the manual for the mysql functions](http://www.php.net/manual/en/function.mysql-errno.php). — hakre, Oct 03 '11 at 12:14
You can use [`mysql_error`](http://www.php.net/manual/en/function.mysql-error.php) to retrieve the error message in case `$result === false`. Note that your database code is horribly unsafe and allows SQL injection. — Kerrek SB, Oct 03 '11 at 12:16
Create a password for the root user! And do not connect to the db as root! — Carlos Campderrós, Oct 03 '11 at 14:32

score 0 · Answer 1 · answered Sep 23 '12 at 13:56

    // returns true if duplicated
function duplicate_catch_error ($database_connection) {
    $mysql_error = array (1022 => "Can't write; duplicate key in table '%s'",1062 => "Duplicate entry '%s' for key %d", 1586 => "Duplicate entry '%s' for key '%s'");  // also allows for the use of sscanf
    if (array_key_exists(mysql_error($database_connection),$mysql_error)) // checks if error is in array
        return true;
    else
        return false;
}

hope this answers your question, also mysql is now depreciated. Use mysqli if you didn't already know :)

score 0 · Answer 2 · answered Oct 03 '11 at 12:14

0

You can use mysql_errno() (or mysqli_errno(), if you use mysqli) to get the error number after a query if it failed (check the return value of mysql_query()). It should be error #1022 (ER_DUP_KEY) according to the mysql error documentation

answered Oct 03 '11 at 12:14

soulmerge

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score 0 · Answer 3 · answered Oct 03 '11 at 12:31

In general, it is better to prevent SQL errors than to catch them. For example, check whether a duplicate exists before you even try to insert the record.

To avoid the issue altogether, you could use an auto-increment field for the ID, and allow the database to assign new numbers automatically. Then the user would never need to enter it, so there would never be a clash due to duplicates.

If you do still need to check for errors, then you can use the mysql_error() or mysql_errno() functions to get the error details.

how to catch error code in PHP

theform.html

result.php

3 Answers3