PHP Basics Tutorial: From Beginner to Master

PHP is a widely used open source server-side scripting language that can handle all tasks in web development. PHP is widely used in web development, especially for its excellent performance in dynamic data processing, so it is loved and used by many developers. In this article, we will explain the basics of PHP step by step to help beginners from getting started to becoming proficient.

1. Basic syntax

PHP is an interpreted language whose code is similar to HTML, CSS and JavaScript. Every PHP statement ends with a semicolon ;, and comments start and end with // or /* */. The following is a simple example:

<?php
//这是注释
echo "Hello World!";
?>

2. Variables and data types

In PHP, variables are used to store various types of data. Variable names begin with $, followed by the name of the variable. The following is a simple example:

<?php
$name = "John";
$age = 25;
echo "My name is ".$name." and I am ".$age." years old.";
?>

PHP supports multiple types of data, including strings, integers, floating point numbers, Boolean values, arrays and objects, etc. The following are some common variables and data types:

$name = "John";  //字符串
$age = 25;  //整数
$price = 1.99;  //浮点数
$isMale = true;  //布尔值
$cities = array("New York", "Los Angeles", "Chicago");  //数组

3. Operators

PHP supports a variety of operators, including arithmetic operators, comparison operators, logical operators and bitwise operators wait. The following are some common operators:

//算术运算符
$x = 10;
$y = 5;
echo $x + $y;  //15
echo $x - $y;  //5
echo $x * $y;  //50
echo $x / $y;  //2

//比较运算符
$x = 10;
$y = "10";
var_dump($x == $y);  //布尔值true，因为值相等
var_dump($x === $y);  //布尔值false，因为类型不同

//逻辑运算符
$x = 10;
$y = 5;
echo $x > 5 && $y > 5;  //true，因为$x大于5且$y大于5
echo $x > 5 || $y > 5;  //true，因为$x大于5或$y大于5

//位运算符
$x = 2;  //二进制为10
$y = 3;  //二进制为11
echo $x & $y;  //2，因为二进制10和11进行与运算后得到10
echo $x | $y;  //3，因为二进制10和11进行或运算后得到11

4. Process control

PHP supports a variety of process control statements, including conditional statements, loop statements, and jump statements. The following are some common flow control statements:

//条件语句
$x = 10;
if ($x > 5) {
  echo "x is greater than 5";
} elseif ($x < 5) {
  echo "x is less than 5";
} else {
  echo "x is equal to 5";
}

//循环语句
$i = 0;
while ($i < 10) {
  echo $i;
  $i++;
}

for ($i = 0; $i < 10; $i++) {
  echo $i;
}

//跳转语句
$x = 10;
switch ($x) {
  case 10:
    echo "x is equal to 10";
    break;
  case 20:
    echo "x is equal to 20";
    break;
  default:
    echo "x is not equal to 10 or 20";
}

5. Functions and arrays

Functions and arrays are commonly used data structures in PHP programming. Functions are used to encapsulate reusable code, and arrays are used to store multiple values. The following are some commonly used functions and arrays:

//函数
function greeting($name) {
  echo "Hello ".$name;
}
greeting("John");

//数组
$cities = array("New York", "Los Angeles", "Chicago");
echo count($cities);  //3
echo $cities[0];  //"New York"

6. File operations and databases

PHP can read and write files, and can connect to the database to store and read data. Pick. The following are some common file operations and database connections:

//文件操作
$filename = "example.txt";
$file = fopen($filename, "w");
fwrite($file, "This is an example");
fclose($file);

//数据库连接
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

$conn = mysqli_connect($servername, $username, $password, $dbname);
if (!$conn) {
  die("Connection failed: " . mysqli_connect_error());
}

$sql = "SELECT * FROM customers";
$result = mysqli_query($conn, $sql);

while ($row = mysqli_fetch_assoc($result)) {
  echo "Name: ".$row["name"]." - Email: ".$row["email"];
}

mysqli_close($conn);

7. Error handling

In PHP programming, error handling is very important. PHP provides some built-in error handling functions and statements that can help us find and solve errors in the program. The following are some common error handling functions and statements:

//错误处理函数
function custom_error($errno, $errstr) {
  echo "<b>Error:</b> [$errno] $errstr";
}

set_error_handler("custom_error");

echo($test);  //出现错误

//错误处理语句
try {
  $conn = new PDO("mysql:host=localhost;dbname=myDB", "username", "password");
  $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
  $sql = "SELECT * FROM customers";
  $result = $conn->query($sql);
  foreach ($result as $row) {
    echo "Name: ".$row["name"]." - Email: ".$row["email"];
  }
} catch(PDOException $e) {
  echo "Error:".$e->getMessage();
}

$conn = null;

Conclusion:

PHP has a wide range of application fields. It can be used in conjunction with languages ​​such as HTML, CSS and JavaScript to create rich Web application. By studying this article, readers should be able to master the basic knowledge of the PHP language and be able to write simple PHP programs. To further improve PHP programming skills, readers can refer to more advanced tutorials to learn advanced technologies such as PHP object-oriented programming, frameworks, and libraries.

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