The best replacement for php 5.5 is hhvm.

The best alternatives to php 5.5 are rated as following:
★★★★★  hhvm

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Speaking about php 5.5, one probably shouldn't forget about apache 2.2.

Other search terms related to php 5.5 and their ratings are:
★★★★★ apache 2.2
★★★★ apache 2.4
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Google Trends

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php 5.5
hhvm