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hello i did 

1.7.6.1

change your prefix "ps_" if you installed with another.. 

mysql -u prestausr -p;
pass--
show databases;
use prestashop-name-here;
UPDATE `ps_configuration` SET `value` = 'staging.example.com' WHERE `ps_configuration`.`id_configuration` = 229;
UPDATE `ps_configuration` SET `value` = 'staging.example.com' WHERE `ps_configuration`.`id_configuration` = 230;
UPDATE `kh_shop_url` SET `domain` = 'staging.example.com', `domain_ssl` = 'staging.example.com' WHERE `kh_shop_url`.`id_shop_url` = 1;
vi /var/www/html/example.com/.htaccess 

/var/www/html/example.com/.htaccess
change all old domain name to new domain name
old.example.com
staging.example.com 

then update apache with correct virtualhost 

hello i did 

1.7.6.1

mysql -u prestausr -p;
pass--
show databases;
use prestashop-name-here;
UPDATE `ps_configuration` SET `value` = 'staging.example.com' WHERE `ps_configuration`.`id_configuration` = 229;
UPDATE `ps_configuration` SET `value` = 'staging.example.com' WHERE `ps_configuration`.`id_configuration` = 230;
UPDATE `pskh_shop_url` SET `domain` = 'staging.example.com', `domain_ssl` = 'staging.example.com' WHERE `pskh_shop_url`.`id_shop_url` = 1;
vi /var/www/html/example.com/.htaccess 

/var/www/html/example.com/.htaccess
change all old domain name to new domain name
old.example.com
staging.example.com 

then update apache with correct virtualhost