replace sed with awk, since sed in mac is too old

src/php/bin/php_extension_doxygen_filter.awk

@@ -20,7 +20,7 @@ function sed_gensub(regexp, replacement, how, target,         cmd_, ret_) { # ar
     gsub(/'/, "'\"'\"'", target);
     gsub(/\\\\/, "\\", regexp);
 
-    cmd_ = "printf '" target "' | sed -E 's/" regexp "/" replacement "/" tolower(how) "'";
+    cmd_ = "printf '" target "' | sed -nE 's/" regexp "/" replacement "/" tolower(how) "p'";
     if (cmd_ | getline ret_ != 1) {
         close(cmd_);
         error = "ERROR: running command: " cmd_ ", ret_: " ret_;
@@ -85,7 +85,7 @@ inDocComment==1 && $0 ~ classLineRegex {
 }
 
 # end of class document
-inDocComment==1 && /\*\// && classDocComment == "" {
+inDocComment==1 && /\*\// && className && classDocComment == "" {
     classDocComment = docComment;
     docComment = "";
 }

src/php/bin/php_extension_to_php_doc.sh

@@ -28,7 +28,8 @@ COMMAND="${1:-}"
 # parse class and methods
 for FILENAME in call_credentials.c call.c channel.c channel_credentials.c \
                 server_credentials.c server.c timeval.c ; do
-    CLASS_NAME=$(sed -E 's/(^|_)(\w)/\U\2/g' <<< "${FILENAME%.*}")
+    CLASS_NAME=$(awk -F _ '{for(i=1; i<=NF; i++) printf "%s", toupper(substr($i,1,1)) substr($i, 2);}' \
+        <<< "${FILENAME%.*}")
     if [[ "$COMMAND" == "generate" ]]; then
         echo Generating lib/Grpc/$CLASS_NAME.php ...
         awk -f php_extension_doxygen_filter.awk ../ext/grpc/$FILENAME \