Which websites offer free PHP functions courses

PHP functions are reusable blocks of code used to organize and simplify code. Create and call functions: Use the function keyword to create a function and pass parameters by value. Parameters and return values: A function can receive parameters and return a value using the return keyword. Scope and visibility: Variables defined inside a function are only visible within the function scope and can be accessed externally using global variables. Anonymous functions: Closures are functions that do not have a name and are typically used for immediate execution. Practical Example: This tutorial provides examples of PHP functions that validate email addresses and trim strings.

PHP Function Practical Tutorial

Introduction

Function is an important concept in the PHP programming language. They can be used to organize code into modules ized and reusable blocks. In this tutorial, we'll explore various aspects of PHP functions and demonstrate their use through practical examples.

Creating and calling functions

To create a function in PHP, use the function keyword, followed by the function name and parameter list (if required):

function myFunction($parameter1, $parameter2) {
  // 函数代码
}

// 调用函数
myFunction("Hello", "World");

Parameter passing and return

Function can receive parameters and return a value. Parameters are passed by value, which means that any changes made to the parameters inside the function will not affect the original variables in the calling function.

To return a value, use return Keywords:

function addNumbers($num1, $num2) {
  return $num1 + $num2;
}

$result = addNumbers(5, 10); // result 将为 15

Scope and visibility

Variables defined inside a function are in the function Visible within the domain and distinct from the variables in the calling function. To make a variable visible outside a function, declare it as global Variable:

$globalVariable = "Global value";

function myFunction() {
  global $globalVariable;
  echo $globalVariable; // 输出 "Global value"
}

Anonymous function

Anonymous functions (also called closures) are not name of the function. They are usually used for immediate execution and do not need to be referenced in the program:

$myClosure = function($input) {
  return $input * 2;
};

$result = $myClosure(10); // result 将为 20

Practical case

Email verification function

Writing a PHP function To verify the validity of an email address:

function validateEmail($email) {
  if (filter_var($email, FILTER_VALIDATE_EMAIL)) {
    return true;
  } else {
    return false;
  }
}

$validEmail = "example@example.com";
$invalidEmail = "invalid.email";

if (validateEmail($validEmail)) {
  echo "Valid email address";
} else {
  echo "Invalid email address";
}

String trim function

Write a PHP function to trim whitespace at both ends of a string:

function trimString($string) {
  return trim($string);
}

$string = "  Hello World   ";
$trimmedString = trimString($string);

echo $trimmedString; // 输出 "Hello World"

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