Something seems to have changed in regards of dependency handling? Or is the upstream tarball somehow broken? Or is there a missing makedep?
This package currently cannot be compiled in a clean chroot or with php-legacy. Former because php isn't a direct or indirect makedepends as depends in package() aren't considered by makepkg. And the latter because the use of php is hardcoded. But as this wasn't a recent change in the PKGBUILD upstream seems to have changed something.

Build error:

==> Starting build()...
make composer
make[1]: Entering directory '/tmp/makepkg/nextcloud-app-cospend/src/cospend-nc-1.6.0'
No composer command available, downloading a copy from the web
mkdir -p /tmp/makepkg/nextcloud-app-cospend/src/cospend-nc-1.6.0/build/tools
curl -sS https://getcomposer.org/installer | php
/bin/sh: line 1: php: command not found
curl: (23) Failure writing output to destination
make[1]: *** [makefile:44: composer] Error 127
make[1]: Leaving directory '/tmp/makepkg/nextcloud-app-cospend/src/cospend-nc-1.6.0'
make: *** [makefile:22: build] Error 2
==> ERROR: A failure occurred in build().

Edit: It seems composer needs to be added as makedepends?

Possible missing build dependency: rsync

==> Starting package()...
rm -rf build
rm -rf /build/nextcloud-app-cospend/pkg/nextcloud-app-cospend/usr/share/webapps/nextcloud/apps
mkdir -p /build/nextcloud-app-cospend/pkg/nextcloud-app-cospend/usr/share/webapps/nextcloud/apps
mkdir -p build
/bin/sh: line 1: rsync: command not found
make: *** [makefile:68: build_release] Error 127
==> ERROR: A failure occurred in package().
    Aborting...