For openSUSE Leap 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:joelgb:branches:devel:languages:php:php74/openSUSE_Leap_15.5/home:joelgb:branches:devel:languages:php:php74.repo
zypper refresh
zypper install php7
For openSUSE Leap 15.4 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:joelgb:branches:devel:languages:php:php74/openSUSE_Leap_15.4/home:joelgb:branches:devel:languages:php:php74.repo
zypper refresh
zypper install php7