(PECL memcached >= 0.1.0)
Memcached::increment — Increment numeric item's value
$key
   [, int $offset = 1
   [, int $initial_value = 0
   [, int $expiry = 0
  ]]] )
   Memcached::increment() increments a numeric item's value
   by the specified offset. If the item's value is not
   numeric, an error will result.
   Memcached::increment() will set the item to the
   initial_value parameter if the key doesn't exist.
  
keyThe key of the item to increment.
offsetThe amount by which to increment the item's value.
initial_valueThe value to set the item to if it doesn't currently exist.
expiryThe expiry time to set on the item.
   Returns new item's value on success or FALSE on failure.
  
Example #1 Memcached::increment() example
<?php
$m = new Memcached();
$m->addServer('localhost', 11211);
$m->set('counter', 0);
$m->increment('counter');
$n = $m->increment('counter', 10);
var_dump($n);
$m->set('counter', 'abc');
$n = $m->increment('counter');
// ^ will fail due to item value not being numeric
var_dump($n);
?>
The above example will output:
int(11) bool(false)