PHP - detect mysql update/insertion failure due to violated unique constraint

Question

This is kind of similar to this question:

PHP MySQL INSERT fails due to unique constraint

but I have a different twist. Let\'s say I have a table with only

Answer 1

From PHP Documentation on the function mysql_errno:

Returns the error number from the last MySQL function, 
or 0 (zero) if no error occurred. 

Also, from MySQL Documentation on Constraint Violation Errors, error code 893 corresponds to:

Constraint violation e.g. duplicate value in unique index

So, we can then write something like this to do the work:

if (!$result) {
    $error_code = mysql_errno();
    if ($error_code == 893) {
        // Duplicate Key
    } else {
        // Some other error.
    }
}