Html-how to store mail template strings elegantly in php

The html template of an email contains both single quotation marks and double quotation marks. how do I write the original strings in a standard format? It feels messy to write in the code with the original string. how can I write the html template of the code that is more elegant and beautiful? it includes both single quotes and double quotation marks? how can I write the original string in a more standard way? It feels messy to write the code with the original string. how can we make the code more elegant and beautiful?

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The html template of an email contains both single quotation marks and double quotation marks. how do I write the original strings in a standard format? It feels messy to write the code with the original string. how can we make the code more elegant and beautiful?

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