What are the things to note about functions in php?

1. Start withfunction##;

2. The function name can start with a letter or an underscore;

3. The function body must be withincurly brackets;

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4.php function There can be no parameters or multiple parameters. If there are multiple parameters, they must be separated bycommas;

##5. The parameter is similar to a variable and should start with$;

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## 6.returnKey Words can make the function return a value;

7. Functions cannot return multiple values;

8. Built-in functions are functions supported by PHP itself by default;

##9. Use function_exists in php to determine whether the function exists;

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10. The function will not be executed immediately when the page is loaded;

##11. The function will only be executed when it is called;

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