Apache JMeter - Apache JMeter™.
Real Load - Real Load - A REST, SOAP, HTML, HTTP, Powershell, SQL performance test tool
Blackfire.io - Blackfire empowers all PHP developers and IT/Ops to continuously verify and improve their app’s performance, throughout its lifecycle, by getting the right information at the right moment.
LoadStorm - Load test websites, web apps, APIs, and mobile apps via the cloud. Use scripts to simulate user behavior for up to a million virtual users. Try it for free!
Sitespeed - Sitespeed.io is an open source tool that helps to analyze and optimize website speed and performance.
WebLOAD - WebLOAD - The most flexible and cost effective software for enterprise load, stress and performance testing, integrated with DevOps processes. Click for details