What are the things to note about functions in php?

1. Start with function##;

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

3. The function body must be within curly brackets;

 1 <?php 2  3 function a_b() { 4  5     echo "hello!!"; 6  7 } 8  9 a_b();10 11 ?>

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

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

1 <?php2 3 function a_b($a,$b) {4     echo $a+$b;5 }6 7 a_b(1,2);8 9 ?>

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

<?phpfunction a_b($a,$b) {return $a+$b;
}$h_b = a_b(1,2);echo $h_b;?>

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;

 1 <?php 2  3 function a_b() { 4     echo "hello"; 5 } 6  7 if (function_exists(&#39;a_b&#39;)) { 8      9     echo &#39;yes&#39;;10 }11 12 ?>

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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