Php notes -- functions (1), php notes -- Functions

Php notes -- functions (1), php notes -- Functions

1. Start with function;

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

3. The function body must be in braces;

 

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

 

4. php functions can have no parameters or multiple parameters. Separate multiple parameters with commas;

5. the parameter is similar to a variable and must start with $;

 

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

 

6. The return keyword allows the function to return values;

 

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

 

7. The function cannot return multiple values;

 

8. built-in functions are supported by php by default;

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

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

 

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

11. The function is executed only when it is called;