Cause a MySQL Deadlock

cause-deadlock.php

<?php 
/*
SQL - 
CREATE TABLE innodb_deadlock_maker(a int primary key) engine=innodb;
*/

$dbA = new DB(); // Get two instances of whatever class you use to handle DB connections
$dbB = new DB(); // and do any initialisation you need

$dbA->connect(); // and open two separate connections
$dbB->connect(); // 

// Then run some SQL using both...

$dbA->sql('set transaction isolation level serializable');
$dbB->sql('set transaction isolation level serializable');

$dbA->sql('delete from innodb_deadlock_maker');
$dbA->sql('insert into innodb_deadlock_maker set a = 2');

$dbA->sql('start transaction');
$dbA->sql('update innodb_deadlock_maker set a = 2 WHERE a = 2');

$dbB->sql('start transaction');
$dbB->sql('update innodb_deadlock_maker set a = 14 WHERE a = 2');

$dbB->sql('COMMIT');
$dbA->sql('COMMIT');

// DEADLOCK!