[php] PHP Try and Catch for SQL Insert

I have a page on my website (high traffic) that does an insert on every page load.

I am curious of the fastest and safest way to (catch an error) and continue if the system is not able to do the insert into MySQL. Should I use try/catch or die or something else. I want to make sure the insert happens but if for some reason it can't I want the page to continue to load anyway.

...
$db = mysql_select_db('mobile', $conn);
mysql_query("INSERT INTO redirects SET ua_string = '$ua_string'") or die('Error #10');
mysql_close($conn);
...

You can implement throwing exceptions on mysql query fail on your own. What you need is to write a wrapper for mysql_query function, e.g.:

// user defined. corresponding MySQL errno for duplicate key entry
const MYSQL_DUPLICATE_KEY_ENTRY = 1022;

// user defined MySQL exceptions
class MySQLException extends Exception {}
class MySQLDuplicateKeyException extends MySQLException {}

function my_mysql_query($query, $conn=false) {
    $res = mysql_query($query, $conn);
    if (!$res) {
        $errno = mysql_errno($conn);
        $error = mysql_error($conn);
        switch ($errno) {
        case MYSQL_DUPLICATE_KEY_ENTRY:
            throw new MySQLDuplicateKeyException($error, $errno);
            break;
        default:
            throw MySQLException($error, $errno);
            break;
        }
    }
    // ...
    // doing something
    // ...
    if ($something_is_wrong) {
        throw new Exception("Logic exception while performing query result processing");
    }

}

try {
    mysql_query("INSERT INTO redirects SET ua_string = '$ua_string'")
}
catch (MySQLDuplicateKeyException $e) {
    // duplicate entry exception
    $e->getMessage();
}
catch (MySQLException $e) {
    // other mysql exception (not duplicate key entry)
    $e->getMessage();
}
catch (Exception $e) {
    // not a MySQL exception
    $e->getMessage();
}

    $sql = "INSERT INTO   customer(FIELDS)VALUES(VALUES)";
    mysql_query($sql);
    if (mysql_errno())
    {
            echo "<script>alert('License already registered');location.replace('customerform.html');</script>";
    }   

if you want to log the error etc you should use try/catch, if you dont; just put @ before mysql_query

edit : you can use try catch like this; so you can log the error and let the page continue to load

function throw_ex($er){  
  throw new Exception($er);  
}  
try {  
mysql_connect(localhost,'user','pass'); 
mysql_select_db('test'); 
$q = mysql_query('select * from asdasda') or throw_ex(mysql_error());  
}  
catch(exception $e) {
  echo "ex: ".$e; 
}

This can do the trick,

function createLog($data){ 
    $file = "Your path/incompletejobs.txt";
    $fh = fopen($file, 'a') or die("can't open file");
    fwrite($fh,$data);
    fclose($fh);
}
$qry="INSERT INTO redirects SET ua_string = '$ua_string'"   
$result=mysql_query($qry);
if(!$result){
    createLog(mysql_error());
}

mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT);

I am not sure if there is a mysql version of this but adding this line of code allows throwing mysqli_sql_exception.
I know, passed a lot of time and the question is already checked answered but I got a different answer and it may be helpful.

$new_user = new User($user);
$mapper = $this->spot->mapper("App\User");

try{
    $id = $mapper->save($new_user);     
}catch(Exception $exception){

    $data["error"] = true;
    $data["message"] = "Error while insertion. Erron in the query";
    $data["data"] = $exception->getMessage();

    return $response->withStatus(409)
    ->withHeader("Content-Type", "application/json")
    ->write(json_encode($data, JSON_UNESCAPED_SLASHES | JSON_PRETTY_PRINT));        
}

if error occurs, you will get something like this->

{
    "error": true,
    "message": "Error while insertion. Erron in the query",
    "data": "An exception occurred while executing 'INSERT INTO \"user\" (...) VALUES (...)' with params [...]:\n\nSQLSTATE[22P02]: Invalid text representation: 7 ERROR:  invalid input syntax for integer: \"default\"" }

with status code:409.

Use any method described in the previous post to somehow catch the mysql error.
Most common is:

$res = mysql_query('bla');
if ($res===false) {
  //error
  die();
}
//normal page

This would also work:

function error() {
  //error
  die()
}
$res = mysql_query('bla') or error();
//normal page

try { ... } catch {Exception $e) { .... } will not work!

Note: Not directly related to you question but I think it would much more better if you display something usefull to the user. I would never revisit a website that just displays a blank screen or any mysterious error message.

Elaborating on yasaluyari's answer I would stick with something like this:

We can just modify our mysql_query as follows:

function mysql_catchquery($query,$emsg='Error submitting the query'){
    if ($result=mysql_query($query)) return $result;
    else throw new Exception($emsg);
}

Now we can simply use it like this, some good example:

try {
    mysql_catchquery('CREATE TEMPORARY TABLE a (ID int(6))');
    mysql_catchquery('insert into a values(666),(418),(93)');
    mysql_catchquery('insert into b(ID, name) select a.ID, c.name from a join c on a.ID=c.ID');
    $result=mysql_catchquery('select * from d where ID=7777777');
    while ($tmp=mysql_fetch_assoc($result)) { ... }
} catch (Exception $e) {
    echo $e->getMessage();
}

Note how beautiful it is. Whenever any of the qq fails we gtfo with our errors. And you can also note that we don't need now to store the state of the writing queries into a $result variable for verification, because our function now handles it by itself. And the same way it handles the selects, it just assigns the result to a variable as does the normal function, yet handles the errors within itself.

Also note, we don't need to show the actual errors since they bear huge security risk, especially so with this outdated extension. That is why our default will be just fine most of the time. Yet, if we do want to notify the user for some particular query error, we can always pass the second parameter to display our custom error message.

Checking the documentation shows that its returns false on an error. So use the return status rather than or die(). It will return false if it fails, which you can log (or whatever you want to do) and then continue.

$rv = mysql_query("INSERT INTO redirects SET ua_string = '$ua_string'");
if ( $rv === false ){
     //handle the error here
}
//page continues loading