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There's FirePHP (I've never used it) but the most straightforward way to inspect variables is Xdebug (supported by PhpStorm, Visual Studio Code and NetBeans).
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SaaSHub
SaaSHub - Software Alternatives and Reviews. SaaSHub helps you find the best software and product alternatives
NOTE:
The number of mentions on this list indicates mentions on common posts plus user suggested alternatives.
Hence, a higher number means a more popular project.