Gulp + WordPress + SASS + Autoprefix + LiveReload

gulpfile.js

var gulp = require('gulp'),
  sass = require('gulp-sass'),
  autoprefixer = require('gulp-autoprefixer'),
  rename = require('gulp-rename'),
  livereload = require('gulp-livereload');

gulp.task('sass', function () {
  return gulp.src('./sass/style.scss')
    .pipe(sass.sync().on('error', sass.logError))
    .pipe(autoprefixer('last 2 versions'))
    .pipe(gulp.dest('./'))
    .pipe(sass.sync({outputStyle: 'compressed'}).on('error', sass.logError))
    .pipe(rename({ suffix: '.min' }))
    .pipe(livereload())
    .pipe(gulp.dest('./'));
});

gulp.task('php', function () {
	return gulp.src('./php/*.php')
	  .pipe(gulp.dest('./'));
});

gulp.task('default', function () {
  livereload.listen(35729);
  gulp.watch('./sass/**/*.scss', gulp.series('sass')).on('change', livereload.changed);
  gulp.watch('**/*.php', gulp.series('php')).on('change', livereload.changed);
});