return TRUE if any/specified field value has changed
@param string $key
@return mixed
975969
public function changed($key=null) {
		if ($key=='_id')
			$key = $this->primary;
		if (method_exists($this->mapper,'changed'))
			return $this->mapper->changed($key);
		else
			trigger_error('method does not exist on mapper',E_USER_ERROR);
	}
720766
public function has($key)
    {
        // For performance, we can use isset,
        // but it will not match if value == 0
        return isset($this->values[$key]) || array_key_exists($key, $this->values);
    }
972886
public function ifExists(string $key): bool
    {
        if ($this->get($key) === false) {
            return false;
        }

        return true;
    }
1293373
public function isDirty($key) {
        if (empty($this->_original[$key]) && empty($this->_attributes[$key])) {
            return false; // No data in either

        } else if (empty($this->_original[$key]) && isset($this->_attributes[$key])) {
            return true; // No original to compare against

        } else if ($this->_attributes[$key] !== $this->_original[$key]) {
            return true; // Current value is different than original
        }

        return false;
    }
76424
public function __isset($key)
    {
        $is_set = false;

        if (!in_array($key, $this->deprecated_properties)) {
            $is_set =
                method_exists($this, $this->getLoaderMethod($key)) ||
                ($this->hasInternalValue($key) &&
                    $this->internal_property_accessible[$key]) ||
                array_key_exists($key, $this->getProtectedPropertyList());
        }

        return $is_set;
    }
998508
public function isValidated($key= '') {
        $unvalidated = array_diff($this->_dirty, $this->_validated);
        if (empty($key)) {
            $validated = (count($unvalidated) > 0);
        } else {
            $validated = !in_array($this->getField($key), $unvalidated);
        }
        return $validated;
    }
1077777
public function isValueChanged($field)
    {
        if (!$this->IsNullable($field)) {
            return false;
        }

        return isset($this->nullableChanged[$field]);
    }
418981
public function getFieldBoost($key)
	{
		return isset($this->_fieldBoosts[$key]) ? $this->_fieldBoosts[$key] : false;
	}
400689
public function has(string $key): bool
    {
        return array_key_exists(strtolower($key), $this->keyMap) &&
            array_key_exists($this->keyMap[strtolower($key)], $this->collection);
    }
646818
public function __isset($key)
    {
        if (method_exists($this, 'get' . Convention::toPascal($key) . 'Attribute')) {
            return true;
        }

        if ($this->keyExists($key)) {
            return true;
        }

        if ($this->relationExists($key)) {
            return true;
        }

        $entity = $this->getEntity();
        if (method_exists($entity, $key)) {
            return true;
        }

        if ($entity->getRepository()->getCache()->tableHasField($entity->getTable(), $key)) {
            return true;
        }

        foreach (get_class_methods($entity) as $method) {
            if (substr($method, 0, 7) == '__isset' && substr($method, -9) == 'Extension') {
                if ($entity->$method($key)) {
                    return true;
                }
            }
        }

        return false;
    }
853401
public function has( $key ) {
		return isset( $this->fields[$key] ) || array_key_exists( $key, $this->fields );
	}
1219550
public function issetItem($key) {
		if (is_array($key)) {
			$key = $this->arrayHashFunction($key);
		}
		
		return isset($this->_data[$key]);
	}
723954
public function has($key)
	{
		$key = $this->id($key);

		if (!isset($this->data[$key]))
		{
			return false;
		}

		$value = $this->data[$key];

		if ($this->isDataExpired($value))
		{
			unset($this->data[$key]);
			return false;
		}

		return true;
	}
557431
public function has($key)
    {
        if (!$this->checkExtraColumns()) {
            return false;
        }

        $this->load();

        return Arr::has($this->data, $key);
    }
1168575
protected function fieldValue(string $key)
    {
        return $this->isBatched()
            ? Arr::get($this->operations, $this->batchIndex.'.'.$key)
            : $this->operations[$key] ?? null;
    }
668969
final public function __isset($key)
	{
		return	array_key_exists($key, $this->_stack) && isset($this->_stack[$key]);
	}
692807
public function offsetExists($key)
    {
        return Arr::accessible($this->value) && Arr::exists($this->value, $key);
    }