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An older version was posted here.

An older version was posted here.

// I am using 'i' as primary key for all hashes
define('ID_KEY', 'i');
/** Local In-Memory Cache: Tables referred by their string names
Storing hashes:
all hashes must have ID_KEY as key
all hashes must have keys other than ID_KEY
and hashes in the same table must have the same key structure (enforced)
Basic CRUD interface + 'readOne' for the first entry + 'realDelete'
arrays packed into json strings, which allows for array values,
e.g. array('key1'=>'val1', 'key2'=> array(1,2,3))
*/
class LocStore {
// assoc. array('table' => array of keys)
private $_keys = array();
// assoc. array of strings indexed by table and id (must be nonempty)
private $_values = array();
/** create entry, enforce the same keys and new id
@param string $table
@param ass. array $hash, must have ID_KEY not null, must have other keys
*/
public function create ($table, array $hash) {
$id = $hash[ID_KEY];
if (! $id) throw new Exception('Id is empty');
unset($hash[ID_KEY]);
if (! $hash) throw new Exception('Empty hash beside id');
// sort by keys alphabetically to ensure the same order for all entries
ksort($hash);
if ( empty($this->_keys[$table]) ) {
// first hash for $table - cache keys
$this->_keys[$table] = array_keys($hash);
} elseif ($this->_keys[$table] != array_keys($hash)) {
throw new Exception('Array keys mismatch: '. json_encode($hash) );
}
if ( isset($this->_values[$table]) && ! empty($this->_values[$table][$id]) ) {
throw new Exception("Id '$id' already exists");
}
$this->_values[$table][$id] = json_encode(array_values($hash));
// for chaining
return $this;
}
// read one entry, empty array if nothing is there
// reset pointer for iteration
public function reset ($table) {
if (! empty($this->_values[$table]) ) {
reset($this->_values[$table]);

}
}
// read next hash and advance pointer
public function readNext ($table) {
if (empty($this->_values[$table])) return array();
$id = key($this->_values[$table]);
next($this->_values[$table]);
if (! $id) return array ();
return $this->read($table, $id);

}
// read one entry if there are some or else return empty array
// in contrast to readNext, the result is always non-empty as long as table has hashes
public function readOne ($table) {
if ( empty($this->_values[$table]) ) return array();
foreach ($this->_values[$table] as $id => $val) {
return $this->read($table, $id);

}
return array();
}
// read by id, empty array if not found
public function read ($table, $id) {
if (! $id) throw new Exception('Id is empty');
if ( empty($this->_values[$table]) || empty($this->_values[$table][$id]) ) return array();
//$keys = $this->_toArray($this->_keys[$table]);
$keys = $this->_keys[$table];
//$values = $this->_toArray($this->_values[$table][$id]);
$values = json_decode($this->_values[$table][$id]);
$result = array_combine($keys, $values);
$result[ID_KEY] = (string) $id;
return $result;
}
// read and delete one nonempty array or return empty if nothing is left
public function readDeleteOne ($table) {
if ( empty($this->_values[$table]) ) return array();
foreach ($this->_values[$table] as $id => $val) {
return $this->readDelete($table, $id);

}
return array();
}
// read and delete by id, empty array if not found
public function readDelete ($table, $id) {
if (! $id) throw new Exception('Id is empty');
if ( empty($this->_values[$table]) || empty($this->_values[$table][$id]) ) return array();
$keys = $this->_keys[$table];
$values = json_decode($this->_values[$table][$id]);
$result = array_combine($keys, $values);
$result[ID_KEY] = (string) $id;
// deletion is here
unset($this->_values[$table][$id]);
return $result;
}
// delete by id, exception if not found
public function delete ($table, $id) {
if (! $id) throw new Exception('Id is empty');
if ( empty($this->_values[$table]) || empty($this->_values[$table][$id]) ) {
throw new Exception('Deleting non-existant entry');
}
unset($this->_values[$table][$id]);
return $this;
}
public function deleteAll ($table) {
$this->_values[$table] = array();
return $this;
}
}

EDIT.

// I am using 'i' as primary key for all hashes
define('ID_KEY', 'i');
/** Local In-Memory Cache: Tables referred by their string names
 * Storing hashes:
 * all hashes must have ID_KEY as key
 * all hashes must have keys other than ID_KEY
 * and hashes in the same table must have the same key structure (enforced)
 * Basic CRUD interface + 'readOne' for the first entry + 'realDelete'
 * arrays packed into json strings, which allows for array values,
 * e.g. array('key1'=>'val1', 'key2'=> array(1,2,3))
 */
class LocStore {
 // assoc. array('table' => array of keys)
 private $_keys = array();
 // assoc. array of strings indexed by table and id (must be nonempty)
 private $_values = array(); 
 /** create entry, enforce the same keys and new id
 * @param string $table
 * @param ass. array $hash, must have ID_KEY not null, must have other keys
 */
 public function create ($table, array $hash) {
 $id = $hash[ID_KEY];
 if (! $id) throw new Exception('Id is empty');
 unset($hash[ID_KEY]);
 if (! $hash) throw new Exception('Empty hash beside id');
 // sort by keys alphabetically to ensure the same order for all entries
 ksort($hash);
 if ( empty($this->_keys[$table]) ) {
 // first hash for $table - cache keys
 $this->_keys[$table] = array_keys($hash);
 } elseif ($this->_keys[$table] != array_keys($hash)) {
 throw new Exception('Array keys mismatch: '. json_encode($hash) );
 }
 if ( isset($this->_values[$table]) && ! empty($this->_values[$table][$id]) ) {
 throw new Exception("Id '$id' already exists");
 }
 $this->_values[$table][$id] = json_encode(array_values($hash));
 // for chaining
 return $this;
 }
 // read one entry, empty array if nothing is there
 // reset pointer for iteration
 public function reset ($table) {
 if (! empty($this->_values[$table]) ) {
 reset($this->_values[$table]); 
 }
 }
 // read next hash and advance pointer
 public function readNext ($table) {
 if (empty($this->_values[$table])) return array();
 $id = key($this->_values[$table]);
 next($this->_values[$table]);
 if (! $id) return array ();
 return $this->read($table, $id); 
 }
 // read one entry if there are some or else return empty array
 // in contrast to readNext, the result is always non-empty as long as table has hashes
 public function readOne ($table) {
 if ( empty($this->_values[$table]) ) return array();
 foreach ($this->_values[$table] as $id => $val) {
 return $this->read($table, $id); 
 }
 return array();
 }
 
 // read by id, empty array if not found
 public function read ($table, $id) {
 if (! $id) throw new Exception('Id is empty');
 if ( empty($this->_values[$table]) || empty($this->_values[$table][$id]) ) return array();
 //$keys = $this->_toArray($this->_keys[$table]);
 $keys = $this->_keys[$table];
 //$values = $this->_toArray($this->_values[$table][$id]);
 $values = json_decode($this->_values[$table][$id]);
 $result = array_combine($keys, $values);
 $result[ID_KEY] = (string) $id;
 return $result;
 }
 // read and delete one nonempty array or return empty if nothing is left
 public function readDeleteOne ($table) {
 if ( empty($this->_values[$table]) ) return array();
 foreach ($this->_values[$table] as $id => $val) {
 return $this->readDelete($table, $id); 
 }
 return array();
 }
 
 // read and delete by id, empty array if not found
 public function readDelete ($table, $id) {
 if (! $id) throw new Exception('Id is empty');
 if ( empty($this->_values[$table]) || empty($this->_values[$table][$id]) ) return array();
 $keys = $this->_keys[$table];
 $values = json_decode($this->_values[$table][$id]);
 $result = array_combine($keys, $values);
 $result[ID_KEY] = (string) $id;
 // deletion is here
 unset($this->_values[$table][$id]);
 return $result;
 }
 
 // delete by id, exception if not found
 public function delete ($table, $id) {
 if (! $id) throw new Exception('Id is empty');
 if ( empty($this->_values[$table]) || empty($this->_values[$table][$id]) ) {
 throw new Exception('Deleting non-existant entry');
 }
 unset($this->_values[$table][$id]);
 return $this;
 }
 
 public function deleteAll ($table) {
 $this->_values[$table] = array();
 return $this;
 }
}

EDIT:

EDIT.

Here is the (only) method from another class using reset and readNext (where $this->_locStore points to the class locStore above):

public function loadChains ($table, $mergeTable, $relKey) {
 $this->_locStore->reset($mergeTable);
 while ( $hash = $this->_locStore->readNext($mergeTable) ) {
 $chain = $this->getChain($mergeTable, $hash[ID_KEY], $relKey);
 $hash[$relKey] = $chain;
 $this->_locStore->create($table, $hash);
 }
 $this->_locStore->deleteAll($mergeTable);
}