Memory Objects


"Movable" memory objects are ones that may be swapped into the cache backend and unloaded from memory when not in active use.

Create movable memory objects using the create([$data]) method of the memory manager:

$memObject = $memoryManager->create($data);

Such objects will be retrieved from the cache and/or memor when accessed again.


"Locked" memory objects will never be swapped to cache or unloaded from memory.

Create locked memory objects using the createLocked([$data]) method of the memory manager:

$memObject = $memoryManager->createLocked($data);

Locked objects implement the same interface as movable objects (Zend\Memory\Container\Interface), and can be used interchangably with movable objects. Use them when you have performance considerations that dictate keeping the information in memory. Access to locked objects is faster, because the memory manager doesn't need to track changes for these objects.

The locked objects class (Zend\Memory\Container\Locked) guarantees virtually the same performance as working with a string variable. The overhead is a single dereference to get the class property.

Memory container 'value' property

Use the memory container (movable or locked) value property to operate with memory object data:

$memObject = $memoryManager->create($data);

echo $memObject->value;

$memObject->value = $newValue;

$memObject->value[$index] = '_';

echo ord($memObject->value[$index1]);

$memObject->value = substr($memObject->value, $start, $length);

An alternative way to access memory object data is to use the getRef(); method.

Memory container interface

Each memory container type provides the following methods:

getRef() method

&getRef() : mixed

The getRef() method returns a reference to the object value.

Movable objects are loaded from the cache at this moment if the object is not already in memory. If the object is loaded from the cache, this might cause swapping of other objects if the memory limit would be exceeded by having all the managed objects in memory.

Tracking changes to data needs additional resources. The getRef() method returns a reference to the string value used to store the data, which is changed directly by user application. Use the getRef() method for value data processing where you want to ensure the data changes without necessarily interacting directly with the memory container:

$memObject = $memoryManager->create($data);

$value = &$memObject->getRef();

for ($count = 0; $count < strlen($value); $count++) {
    $char = $value[$count];
    // ...

touch() method

touch() : void

The touch() method should be used in conjunction with getRef(). It signals that object value has been changed:

$memObject = $memoryManager->create($data);

$value = &$memObject->getRef();

for ($count = 0; $count < strlen($value); $count++) {
    // ...
    if ($condition) {
        $value[$count] = $char;
    // ...


lock() method

lock() : void

The lock() methods locks the object in memory. It should be used to prevent swapping of the object. Normally, this is not necessary, because the memory manager uses an intelligent algorithm to choose candidates for swapping. But if you know that at a specific point in the code an object should not be swapped, you may lock it.

Locking objects in memory also guarantees that the reference returned by the getRef() method is valid until you unlock the object:

$memObject1 = $memoryManager->create($data1);
$memObject2 = $memoryManager->create($data2);


$value1 = &$memObject1->getRef();
$value2 = &$memObject2->getRef();

for ($count = 0; $count < strlen($value2); $count++) {
    $value1 .= $value2[$count];


unlock() method

unlock() : void

The unlock() method unlocks object when it's no longer necessary to be locked. See the example above.

isLocked() method

isLocked() : bool

The isLocked() method can be used to check if object is locked. It returns true if the object is locked, or false if it is not locked. This is always true for "locked" objects, and may be either true or false for "movable" objects.

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