Merge pull request #83 from glensc/sc2

Linter: Fix SC2223

Author: glensc

install-extensions.sh

@@ -2,10 +2,9 @@
 
 set -xeu
 
-: ${TRAVIS_PHP_VERSION=7.4}
-: ${TIDEWAYS_VERSION=4.1.4}
-: ${TIDEWAYS_XHPROF_VERSION=5.0.2}
-: ${PHP_VERSION=${TRAVIS_PHP_VERSION}}
+: "${TIDEWAYS_VERSION:=4.1.4}"
+: "${TIDEWAYS_XHPROF_VERSION:=5.0.2}"
+: "${PHP_VERSION:=7.4}"
 
 die() {
 	echo >&2 "ERROR: $*"