Fatal error: Declaration of CRMCoreContactController::save($contact) must be compatible with EntityAPIController::save - drupal-7

Question

I recently installed CRM Core and all of its missing modules needed to run it. Sadly I need this module for the project that I am working on but the second I installed them I got this error.
Fatal error: Declaration of CRMCoreContactController::save($contact) must be compatible with EntityAPIController::save($entity, ?DatabaseTransaction $transaction = NULL) in /opt/lampp/htdocs/drupal/modules/crm_core/modules/crm_core_contact/includes/crm_core_contact.controller.inc on line 111
I went back in the code and I couldn't see what to change. Line 111 is the ver last line of the code. Ill paste the code as well maybe someone out there knows how to solve this, please.
<?php
/**
* CRM Contact Entity Class.
*/
class CRMCoreContactEntity extends Entity {
protected function defaultLabel() {
return crm_core_contact_label($this);
}
protected function defaultUri() {
return array(
'path' => 'crm-core/contact/' . $this->identifier(),
'options' => array(
'absolute' => TRUE,
),
);
}
/**
* Method for de-duplicating contacts.
*
* Allows various modules to identify duplicate contact records through
* hook_crm_core_contact_match. This function should implement it's
* own contact matching scheme.
*
* #return array
* Array of matched contact IDs.
*/
public function match() {
$checks = & drupal_static(__FUNCTION__);
$matches = array();
if (!isset($checks->processed)) {
$checks = new stdClass();
$checks->engines = module_implements('crm_core_contact_match');
$checks->processed = 1;
}
// Pass in the contact and the matches array as references.
// This will allow various matching tools to modify the contact
// and the list of matches.
$values = array(
'contact' => &$this,
'matches' => &$matches,
);
foreach ($checks->engines as $module) {
module_invoke($module, 'crm_core_contact_match', $values);
}
// It's up to implementing modules to handle the matching logic.
// Most often, the match to be used should be the one
// at the top of the stack.
return $matches;
}
}
/**
* #file
* Controller class for contacts.
*
* This extends the DrupalDefaultEntityController class, adding required
* special handling for contact objects.
*/
class CRMCoreContactController extends EntityAPIController {
public $revisionKey = 'vid';
public $revisionTable = 'crm_core_contact_revision';
/**
* Create a basic contact object.
*/
public function create(array $values = array()) {
global $user;
$values += array(
'contact_id' => '',
'vid' => '',
'uid' => $user->uid,
'created' => REQUEST_TIME,
'changed' => REQUEST_TIME,
);
return parent::create($values);
}
/**
* Update contact object before saving revision.
*/
protected function saveRevision($entity) {
if (!isset($entity->log)) {
$entity->log = '';
}
$entity->is_new_revision = TRUE;
$entity->uid = $GLOBALS['user']->uid;
return parent::saveRevision($entity);
}
/**
* Updates 'changed' property on save.
*/
public function save($contact) {
$contact->changed = REQUEST_TIME;
// Storing formatted contact label for autocomplete lookups.
$contact->name = crm_core_contact_label($contact);
return parent::save($contact);
}
}

Answer 1

Changing
public function save($contact)
to
public function save($contact, DatabaseTransaction $transaction = NULL)
should work.

Answer 2

You need to switch from PHP 7.x+ to PHP 5.6. This will resolve this error.
Can't give you more advice on how to downgrade without more details on what system you're running but there are many guides out there on this topic.