How to convert string to integer (PHP & MySQL)

Here is a type conversion from string to int, the same way, with PHP & MySQL.
Basically, you can change the type of your string by adding 0.

PHP

$myVar = "13";
var_dump($myVar); // string '13' (length=2)
$myVar= $myVar +0; // or $myVar+= 0
var_dump($myVar); // int 13

MySQL

SELECT * FROM stop_times LEFT JOIN stops ON stop_times.stop_id=stops.stop_id WHERE stop_times.trip_id=2755013 ORDER BY stop_times.stop_sequence+0 ASC

In this example, the stop_sequence is stored as a Varchar, without the conversion, you'll have the stop_sequence in the following order : 1, 10, 11, 12, etc.

Why using that tips ?

Edit: I wrote this tips in 2015 and I don't really think it has a real use case other than showing how PHP convert string to int internally.
You can read more about String conversion to numbers from php.net

Others ways to do the type conversion

In PHP, you can use the intval() function or cast your variable with (int) :

$myVar = "13";
var_dump($myVar); // string '13' (length=2)
$myVar= intval($myVar);
var_dump($myVar); // int 13

$myVar = "13";
var_dump($myVar); // string '13' (length=2)
$myVar= (int)$myVar;
var_dump($myVar); // int 13

In SQL, you can use the CAST() function :

SELECT * FROM stop_times LEFT JOIN stops ON stop_times.stop_id=stops.stop_id WHERE stop_times.trip_id=2755013 ORDER BY CAST(stop_times.stop_sequence AS UNSIGNED INTEGER) ASC