This is software will be directly citable via Zenodo soon. However, these are relevant publications that you can cite in the mean time:
@article{DBLP:journals/scp/HillsKV17,
author = {Mark Hills and
Paul Klint and
Jurgen J. Vinju},
title = {Enabling {PHP} software engineering research in Rascal},
journal = {Sci. Comput. Program.},
volume = {134},
pages = {37--46},
year = {2017},
url = {https://doi.org/10.1016/j.scico.2016.05.003},
doi = {10.1016/j.scico.2016.05.003},
timestamp = {Wed, 14 Jun 2017 20:29:38 +0200},
biburl = {https://dblp.org/rec/journals/scp/HillsKV17.bib},
bibsource = {dblp computer science bibliography, https://dblp.org}
}@inproceedings{DBLP:conf/scam/Anderson017,
author = {David Anderson and
Mark Hills},
title = {Supporting Analysis of {SQL} Queries in {PHP} AiR},
booktitle = {17th {IEEE} International Working Conference on Source Code Analysis
and Manipulation, {SCAM} 2017, Shanghai, China, September 17-18, 2017},
pages = {153--158},
publisher = {{IEEE} Computer Society},
year = {2017},
url = {https://doi.org/10.1109/SCAM.2017.23},
doi = {10.1109/SCAM.2017.23},
timestamp = {Fri, 24 Mar 2023 00:02:43 +0100},
biburl = {https://dblp.org/rec/conf/scam/Anderson017.bib},
bibsource = {dblp computer science bibliography, https://dblp.org}
}@inproceedings{DBLP:conf/wcre/AndersonH17,
author = {David Anderson and
Mark Hills},
editor = {Martin Pinzger and
Gabriele Bavota and
Andrian Marcus},
title = {Query Construction Patterns in {PHP}},
booktitle = {{IEEE} 24th International Conference on Software Analysis, Evolution
and Reengineering, {SANER} 2017, Klagenfurt, Austria, February 20-24,
2017},
pages = {452--456},
publisher = {{IEEE} Computer Society},
year = {2017},
url = {https://doi.org/10.1109/SANER.2017.7884652},
doi = {10.1109/SANER.2017.7884652},
timestamp = {Fri, 24 Mar 2023 00:04:44 +0100},
biburl = {https://dblp.org/rec/conf/wcre/AndersonH17.bib},
bibsource = {dblp computer science bibliography, https://dblp.org}
}@inproceedings{DBLP:conf/iwpc/Hills16,
author = {Mark Hills},
title = {Navigating the WordPress plugin landscape},
booktitle = {24th {IEEE} International Conference on Program Comprehension, {ICPC}
2016, Austin, TX, USA, May 16-17, 2016},
pages = {1--10},
publisher = {{IEEE} Computer Society},
year = {2016},
url = {https://doi.org/10.1109/ICPC.2016.7503709},
doi = {10.1109/ICPC.2016.7503709},
timestamp = {Thu, 23 Mar 2023 23:57:51 +0100},
biburl = {https://dblp.org/rec/conf/iwpc/Hills16.bib},
bibsource = {dblp computer science bibliography, https://dblp.org}
}@inproceedings{DBLP:conf/kbse/Hills15,
author = {Mark Hills},
editor = {Myra B. Cohen and
Lars Grunske and
Michael Whalen},
title = {Variable Feature Usage Patterns in {PHP} {(T)}},
booktitle = {30th {IEEE/ACM} International Conference on Automated Software Engineering,
{ASE} 2015, Lincoln, NE, USA, November 9-13, 2015},
pages = {563--573},
publisher = {{IEEE} Computer Society},
year = {2015},
url = {https://doi.org/10.1109/ASE.2015.72},
doi = {10.1109/ASE.2015.72},
timestamp = {Fri, 24 Mar 2023 00:02:37 +0100},
biburl = {https://dblp.org/rec/conf/kbse/Hills15.bib},
bibsource = {dblp computer science bibliography, https://dblp.org}
}@inproceedings{DBLP:conf/oopsla/Hills15,
author = {Mark Hills},
editor = {Harry Xu and
Walter Binder},
title = {Supporting {PHP} dynamic analysis in {PHP} AiR},
booktitle = {Proceedings of the 13th International Workshop on Dynamic Analysis,
WODA@SPLASH 2015, Pittsburgh, PA, USA, October 26, 2015},
pages = {37--38},
publisher = {{ACM}},
year = {2015},
url = {https://doi.org/10.1145/2823363.2823373},
doi = {10.1145/2823363.2823373},
timestamp = {Fri, 14 Apr 2023 23:05:46 +0200},
biburl = {https://dblp.org/rec/conf/oopsla/Hills15.bib},
bibsource = {dblp computer science bibliography, https://dblp.org}
}@inproceedings{DBLP:conf/wcre/000115,
author = {Mark Hills},
editor = {Yann{-}Ga{\"{e}}l Gu{\'{e}}h{\'{e}}neuc and
Bram Adams and
Alexander Serebrenik},
title = {Evolution of dynamic feature usage in {PHP}},
booktitle = {22nd {IEEE} International Conference on Software Analysis, Evolution,
and Reengineering, {SANER} 2015, Montreal, QC, Canada, March 2-6,
2015},
pages = {525--529},
publisher = {{IEEE} Computer Society},
year = {2015},
url = {https://doi.org/10.1109/SANER.2015.7081870},
doi = {10.1109/SANER.2015.7081870},
timestamp = {Fri, 24 Mar 2023 00:04:45 +0100},
biburl = {https://dblp.org/rec/conf/wcre/000115.bib},
bibsource = {dblp computer science bibliography, https://dblp.org}
}@inproceedings{DBLP:conf/csmr/HillsK14,
author = {Mark Hills and
Paul Klint},
editor = {Serge Demeyer and
Dave W. Binkley and
Filippo Ricca},
title = {{PHP} AiR: Analyzing {PHP} systems with Rascal},
booktitle = {2014 Software Evolution Week - {IEEE} Conference on Software Maintenance,
Reengineering, and Reverse Engineering, {CSMR-WCRE} 2014, Antwerp,
Belgium, February 3-6, 2014},
pages = {454--457},
publisher = {{IEEE} Computer Society},
year = {2014},
url = {https://doi.org/10.1109/CSMR-WCRE.2014.6747217},
doi = {10.1109/CSMR-WCRE.2014.6747217},
timestamp = {Fri, 24 Mar 2023 00:02:40 +0100},
biburl = {https://dblp.org/rec/conf/csmr/HillsK14.bib},
bibsource = {dblp computer science bibliography, https://dblp.org}
}@inproceedings{DBLP:conf/kbse/HillsKV14,
author = {Mark Hills and
Paul Klint and
Jurgen J. Vinju},
editor = {Ivica Crnkovic and
Marsha Chechik and
Paul Gr{\"{u}}nbacher},
title = {Static, lightweight includes resolution for {PHP}},
booktitle = {{ACM/IEEE} International Conference on Automated Software Engineering,
{ASE} '14, Vasteras, Sweden - September 15 - 19, 2014},
pages = {503--514},
publisher = {{ACM}},
year = {2014},
url = {https://doi.org/10.1145/2642937.2643017},
doi = {10.1145/2642937.2643017},
timestamp = {Tue, 06 Nov 2018 16:58:23 +0100},
biburl = {https://dblp.org/rec/conf/kbse/HillsKV14.bib},
bibsource = {dblp computer science bibliography, https://dblp.org}
}@inproceedings{DBLP:conf/issta/HillsKV13,
author = {Mark Hills and
Paul Klint and
Jurgen J. Vinju},
editor = {Mauro Pezz{\`{e}} and
Mark Harman},
title = {An empirical study of {PHP} feature usage: a static analysis perspective},
booktitle = {International Symposium on Software Testing and Analysis, {ISSTA}
'13, Lugano, Switzerland, July 15-20, 2013},
pages = {325--335},
publisher = {{ACM}},
year = {2013},
url = {https://doi.org/10.1145/2483760.2483786},
doi = {10.1145/2483760.2483786},
timestamp = {Sun, 02 Oct 2022 16:10:12 +0200},
biburl = {https://dblp.org/rec/conf/issta/HillsKV13.bib},
bibsource = {dblp computer science bibliography, https://dblp.org}
}