The difference between three string delimiters in PHP

The difference between single quotes, double quotes, <<< is as follows:

Single quotes: Variables contained in single quotes will not be parsed, but will be output as is.

                                                                                            $book                                                     $book                      

                                                                                                                          $book =            Contains defined variables, PHP will also parse them.

  Start with <<< plus any name you like, such as <<

                                                                                                                                                                                                                                                                                               .

 HEREDOC;

?>

Based on the above, it can be seen that the execution efficiency of single quotes is higher than the latter two. Therefore, it should be considered appropriately during use.

type="text/javascript">AjaxAction("/Ajax.Asp?Action=ShowSpecial&LogID=33&ShowType=1");

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