Use Memcache::replace() first instead of Memcache::set(): http://docs.php.net/manual/en/memcache.replace.php#100023

till · fabpot · commit 962f975a6f5b · 2012-04-18T12:17:02.000+02:00
diff --git a/src/Symfony/Component/HttpFoundation/Session/Storage/Handler/MemcacheSessionHandler.php b/src/Symfony/Component/HttpFoundation/Session/Storage/Handler/MemcacheSessionHandler.php
@@ -117,7 +117,10 @@ public function read($sessionId)
      */
     public function write($sessionId, $data)
     {
-        return $this->memcache->set($this->prefix.$sessionId, $data, 0, $this->memcacheOptions['expiretime']);
+        if (!$this->memcache->replace($this->prefix.$sessionId, $data, 0, $this->memcacheOptions['expiretime'])) {
+            return $this->memcache->set($this->prefix.$sessionId, $data, 0, $this->memcacheOptions['expiretime']);
+        }
+        return true;
     }
 
     /**

Original file line number	Diff line number	Diff line change
`@@ -117,7 +117,10 @@ public function read($sessionId)`
`117`	`117`	`*/`
`118`	`118`	`public function write($sessionId, $data)`
`119`	`119`	`{`
`120`		`- return $this->memcache->set($this->prefix.$sessionId, $data, 0, $this->memcacheOptions['expiretime']);`
	`120`	`+ if (!$this->memcache->replace($this->prefix.$sessionId, $data, 0, $this->memcacheOptions['expiretime'])) {`
	`121`	`+ return $this->memcache->set($this->prefix.$sessionId, $data, 0, $this->memcacheOptions['expiretime']);`
	`122`	`+ }`
	`123`	`+ return true;`
`121`	`124`	`}`
`122`	`125`
`123`	`126`	`/**`