minor #14821 Update introduction.rst (falnyr)

This PR was submitted for the 5.2 branch but it was merged into the 4.4 branch instead.

Discussion
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Update introduction.rst

PHP 5.5 is no longer supported

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Commits
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0d09b1f Update introduction.rst

Author: javiereguiluz

create_framework/introduction.rst

@@ -62,7 +62,7 @@ Before You Start
 
 Reading about how to create a framework is not enough. You will have to follow
 along and actually type all the examples included in this tutorial. For that,
-you need a recent version of PHP (5.5.9 or later is good enough), a web server
+you need a recent version of PHP (7.4 or later is good enough), a web server
 (like Apache, nginx or PHP's built-in web server), a good knowledge of PHP and
 an understanding of Object Oriented programming.