update PHP release to not fail on existing tag

php/ext/google/protobuf/package.xml

@@ -10,8 +10,8 @@
   <email>protobuf-opensource@google.com</email>
   <active>yes</active>
  </lead>
- <date>2022-03-15</date>
+ <date>2022-03-18</date>
- <time>21:10:15</time>
+ <time>11:10:15</time>
  <version>
   <release>3.20.0RC2</release>
   <api>3.20.0</api>

php/release.sh

@@ -30,7 +30,11 @@ mv ../protobuf/composer.json composer.json
 sed -i 's|php/src|src|g' composer.json
 git add .
 git commit -m "$VERSION"
+if [ $(git tag -l "$VERSION") ]; then
+  echo "tag $VERSION already exists"
+else
   git tag "$VERSION"
+fi
 popd
 
 # Clean up