PHP functions

PHP functions are similar to other programming languages. A function is a piece of code that takes one or more inputs in the parameter form, then performs some processing and returns a value.

The previous chapter is familiar with functions like fopen () and fread () . These are built-in functions, but PHP also gives you the option to create your own functions.

This chapter will help you understand the following two sections:

1. Create a function in PHP
2. Call a function in PHP

In fact, you almost don't need to create PHP functions yourself, because there are already over 1000 built-in functions in the library to handle different tasks and you just need to call them according to your needs.

Create functions in PHP

In PHP, it is very simple to create your own function. Suppose you want to create a function, this function will simply write a message in the browser when you call it. The following example will create a QTMMessage () function and call it after creating.

Note that while creating a function, the function name should start with the function keyword and all PHP code should be put in {and} as follows:

 Đây là hàm PHP  php /* Định nghĩa hàm PHP */ function QTMMessage () { echo "Chúc các bạn học PHP thật tốt!" ; } /* Gọi hàm PHP */ QTMMessage (); ?> 

Save the program in a file named test.php in htdocs , then open the browser and type the address http:/// localhost: 8080 / test.php to see the result.

 Wish you all good PHP students! 

Function with parameters in PHP

PHP gives you the option to pass parameters into a function. You can use as many parameters as you like. These parameters work as variables in the function. The following example uses two integer parameters and their sum and prints.

 Hàm PHP với tham số  php function hamTimTong ( $num1 , $num2 ) { $sum = $num1 + $num2 ; echo "Tổng của hai số là: $sum" ; } hamTimTong ( 15 , 35 ); ?> 

Save the above program in a file named test.php in htdocs , then open the browser and type the address http:/// localhost: 8080 / test.php will result:

 The sum of two numbers is: 50 

Pass parameters by reference in PHP

It is possible to pass parameters to functions by reference. That is, a reference to the variable manipulated by the function instead of copying a value of that variable.

Any changes made to a parameter in these cases will change the value of the original variable. You can pass a parameter by reference by adding a symbol & for the variable name in: function call or function definition.

The following example describes these two cases:

 Truyền tham số bằng tham chiếu trong PHP  php function themNam ( $num ) { $num += 5 ; } function themSau ( & $num ) { $num += 6 ; } $orignum = 10 ; themNam ( $orignum ); echo "Giá trị biến orignum là $orignum
" ; themSau ( $orignum ); echo "Giá trị biến orignum là $orignum
" ; ?> 

Save the above program in a file named test.php in htdocs , then open the browser and type the address http:/// localhost: 8080 / test.php will result:

 The value of orignum is 10 
 The value of the orignum variable is 16 

The function returns the value in PHP

A function can return a value by using the return statement associated with a value or an object. The return in PHP function stops the execution of the function and sends the value back to the calling code.

You can return more than one value from a function by using the return array (1,2,3,4) .

The following example takes two integer parameters and calculates their total value, then returns the result for the calling program. Note that the return keyword is used to return a value from a function.

 Hàm trả về giá trị trong PHP  php function hamTimTong ( $num1 , $num2 ) { $sum = $num1 + $num2 ; return $sum ; } $return_value = hamTimTong (2 0 , 79 ); echo "Giá trị hàm trả về là : $return_value" ; ?> 

Save the above program in a file named test.php in htdocs , then open the browser and type the address http:/// localhost: 8080 / test.php will result:

 The return function value is : 99 

Set the default value for the function parameter in PHP

You can set a default value for the parameter if the caller does not pass the value to it.

The following function prints the Default string in the case of not passing any value to this function.

 Đặt giá trị mặc định cho tham số  php function inTB ( $param = "Mặc định" ) { print $param ; } inTB ( "Truyền tham số cho hàm
" ); inTB (); ?> 

Save the above program in a file named test.php in htdocs , then open the browser and type the address http:/// localhost: 8080 / test.php will result:

 Pass parameters to functions 
 Default 

Call the dynamic function in PHP

In PHP, you can assign function names as strings to variables and then treat these variables as if you had the function name itself. The following example describes this behavior:

 Gọi hàm động trong PHP  php function sayChao () { echo "Xin chào!
" ; } $function_holder = "sayChao" ; $function_holder (); ?> 

Save the above program in a file named test.php in htdocs , then open the browser and type the address http:/// localhost: 8080 / test.php will result:

 Hello! 

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