How to deal with nested php pages

Web page nesting php in a large web page such as. php, which needs to be embedded into a small web page B. php: use a form to add and store data in a small webpage. in php, the whole process of returning results is that large webpages are not affected. how can this problem be achieved ???, The simplest method is to use iframe to introduce small webpages and JAVASCRIPT to control interactive operations.
For example,. php, which needs to be embedded into a small web page B. php: use a form to add and store data in a small webpage. php returns results
In the whole process, large webpages are not affected. how can this problem be achieved ???

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The simplest method is to use iframe to introduce small webpages and JAVASCRIPT to control interactive operations.
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Ajax
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Iframe is embedded into B. php...

The location control of iframe is used to refresh and load all pages.