What are the two types of php functions?

The real power of PHP comes from its functions. Functions are divided into built-in functions and custom functions.

Built-in functions

The so-called PHP built-in functions are functions that have been defined in the library of the PHP program, such as echo, mysql_connect, include_once etc., just like the system functions in VC, such as cout, etc.

In PHP, more than 1,000 built-in functions are provided.

Custom functions

In addition to the built-in PHP functions, we can create our own functions.

● Functions are reusable blocks of code used to complete a specific task in the program;

● Functions can make the program more modular and have a good structure;

● After the function is defined, it can be called repeatedly in the program;

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

● Function will only be executed when called.

Creating user-defined functions in PHP

User-defined function declarations begin with the words "function":

Syntax

function functionName() {
  被执行的代码;
}

Note: Function names can start with letters or underscores (not numbers). Function names are not case sensitive.

Tip: The function name should reflect the task performed by the function.

Example:

We create a function named "writeMsg()". An opening brace ({) indicates the beginning of a function's code, while a closing brace (}) indicates the end of the function. This function outputs "Hello world!". If you need to call this function, just use the function name:

<?php
function sayhi() {
   echo "Hello world!";
}

sayhi();
?>

Output:

Hello world!

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