I. Hola Jorge, en mi caso no soy conocedor, pero como lector habitual deseaba trasladarle un poco de información sobre este tema, recogida en parte de consultas anteriores, por si le fuese de utilidad mientras le atiende de primera mano un experto o programador. Le ruego me disculpe tanta imprecisión y todas las molestias de lectura. Ánimo.
https://stackoverflow-com.translate.goog/questions/27212483/how-to-transfer-login-information-and-automatically-log-to-another-website-when?_x_tr_sl=en&_x_tr_tl=es&_x_tr_hl=es&_x_tr_pto=sc
https://stackoverflow.com/questions/4091677/php-authentication-with-multiple-domains-and-subdomains
https://es.stackoverflow.com/questions/179989/como-puedo-pasar-de-un-sitio-a-otro-manteniendo-login-desdel-sitio-main
https://es.stackoverflow.com/questions/420788/c%C3%B3mo-compartir-la-sesi%C3%B3n-de-php-entre-distintos-or%C3%ADgenes
https://stackoverflow.com/questions/14588050/php-session-login-crossing-between-sites-on-same-server
https://stackoverflow-com.translate.goog/questions/4306728/how-to-create-a-shared-login-service-across-multiple-domains?_x_tr_sl=en&_x_tr_tl=es&_x_tr_hl=es&_x_tr_pto=sc
https://softwareengineering-stackexchange-com.translate.goog/questions/200511/how-to-securely-implement-auto-login?_x_tr_sl=en&_x_tr_tl=es&_x_tr_hl=es&_x_tr_pto=sc
https://es.stackoverflow.com/questions/49418/redireccionar-acceso-con-sesiones
https://stackoverflow.com/questions/35235920/php-login-in-one-domain-then-using-the-session-in-another-one
https://stackoverflow.com/questions/29676823/single-login-for-multiple-platforms-on-different-websites
http://www.webassist.com/forums/posts.php?id=34809
https://stackoverflow.com/questions/8614480/automatically-login-to-current-website-if-user-is-logged-in-to-another-website
https://community-jaspersoft-com.translate.goog/forums/topic/45683-automatic-login-from-a-application-with-php-on-another-sub-domain/?_x_tr_sl=en&_x_tr_tl=es&_x_tr_hl=es&_x_tr_pto=sc
https://www.youtube.com/watch?v=6MvB3mSWirQ
https://softwareengineering-stackexchange-com.translate.goog/questions/118801/sharing-authentication-across-subdomains-using-cookies?_x_tr_sl=en&_x_tr_tl=es&_x_tr_hl=es&_x_tr_pto=sc