A Beginner's Guide to Basic PHP Syntax-PHP Tutorial-php.cn

A Beginner's Guide to Basic PHP Syntax

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Release： 2023-06-22 18:32:01

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PHP is an open source server-side programming language for writing Web applications. It has the advantages of being easy to learn, flexible, and highly efficient in development, so it is widely used in Web development.

However, learning the basic syntax of PHP is often a difficult process for beginners. Therefore, this guide will provide you with introductory knowledge of PHP basic syntax, allowing you to easily master the basics of PHP

Basic form of PHP
PHP files must have a .php suffix, as follows: A basic PHP program example:

<!DOCTYPE html>
<html>
<head>
    <title>PHP示例程序</title>
</head>
<body>
    <?php echo "Hello, PHP!"; ?>
</body>
</html>

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In the above code, the PHP code is included between the <?php ?> tags and can be embedded in the HTML tags.

Variables
In PHP, variables are used to store variable values. When defining a variable, it needs to start with the $ symbol, followed by the variable name and initial value (optional).

<?php
$name = "Mike";
$age = 24;
?>

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Variable names are case-sensitive and must meet the following rules:

Variable names must start with a letter or underscore
Variable names can only contain Letters, numbers and underscores
Variable names cannot contain spaces

Data type
PHP supports multiple data types, such as strings, integers, floating point numbers, Boole et al.

String: expressed in quotation marks. The difference between single quotes and double quotes is that variables in single quotes will be treated as strings, while variables in double quotes will be parsed.

$name = 'Mike';
$message = "Hello, $name!";

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Integer: can be expressed in decimal, octal, or hexadecimal.

$number1 = 10;
$number2 = 012; // 八进制
$number3 = 0xA; // 十六进制

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Floating point number: a number with a decimal point.

$float1 = 3.14;
$float2 = 1.0e3; // 必须有小数点

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Boolean: The value is true or false.

$is_true = true;
$is_false = false;

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Operators
PHP supports common operators, such as addition, subtraction, multiplication and division, logical operations, comparison operations, etc.

Addition, subtraction, multiplication and division: similar to other programming languages.

$a = 10;
$b = 5;
$c = $a + $b; // 15
$d = $a - $b; // 5
$e = $a * $b; // 50
$f = $a / $b; // 2

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Comparison operation: used to determine whether two values are equal, large, etc. The return value is of Boolean type.

$a = 10;
$b = 5;
$c = 10;
var_dump($a == $b); // false
var_dump($a != $b); // true
var_dump($a === $c); // true
var_dump($a !== $c); // false
var_dump($a > $b); // true
var_dump($a < $b); // false
var_dump($a >= $b); // true
var_dump($a <= $b); // false

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Logical operations: used to combine multiple conditions, and the return value is of Boolean type.

$a = 10;
$b = 5;
$c = 1;
var_dump(($a > $b) && ($c > $b)); // true
var_dump(($a < $b) || ($c > $b)); // true
var_dump(!($a < $b)); // true

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Control statements
Control statements in PHP can be used to control the flow of programs, such as conditional statements, loop statements, etc.

Conditional statements: used to execute different code blocks based on different conditions.

$a = 10;
$b = 5;
if ($a > $b) {
    echo 'a > b';
} elseif ($a == $b) {
    echo 'a == b';
} else {
    echo 'a < b';
}

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Loop statement: used to repeatedly execute a piece of code.

$arr = array('apple', 'banana', 'orange');
foreach ($arr as $value) {
    echo $value;
}

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Among them, $value represents each element in the array. In addition, there are loop statements similar to while, do...while, which are skipped here.

Function
A function is an encapsulated block of code that can be reused. In PHP, you can use the functions provided in the function library or define your own functions.

Custom function: Use the function keyword to define a function.

function say_hello($name) {
    echo "Hello, $name!";
}

say_hello('Mike'); // Hello, Mike!

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Built-in functions: PHP provides many built-in functions, such as string-related functions, array-related functions, file-related functions, etc. These functions can quickly complete common tasks and improve development efficiency.

$name = 'Mike';
$length = strlen($name); // 计算字符串长度
$upper = strtoupper($name); // 将字符串转换为大写
echo $length, $upper; // 输出8MIKE

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The above is an introductory guide to the basic syntax of PHP. Of course, there are many details and knowledge to learn. I hope this guide is helpful and allows you to quickly get started with PHP development.

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