Detailed explanation of the branch structure of php program

In programming, the branch structure of a program is a very common structure. It can select different execution paths according to different conditions, making the program's functions more flexible and practical. In the PHP programming language, there is also a syntax for implementing program branch structures. Let us take a look at it below.

1. if statement

The if statement is the most basic branch structure statement, which can select different execution paths based on conditions. The syntax of the if statement is as follows:

if(条件表达式){
    //条件为真时执行的代码
}else{
    //条件为假时执行的代码
}

Among them, the conditional expression can be any value that returns a Boolean value, such as variables, constants, function return values, etc. The code block in if is executed when the conditional expression is true, otherwise the code block in else is executed.

For example, when we need to determine whether a variable is equal to 5:

$a = 5;
if($a == 5){
    echo "a等于5";
}else{
    echo "a不等于5";
}

The output result is:

a等于5

2. switch statement

## The #switch statement is also a program branching structure, which can execute different statement blocks based on different values. The syntax of the switch statement is as follows:

switch(表达式){
    case 值1：
        //执行代码块1
        break;
    case 值2：
        //执行代码块2
        break;
    ...
    default:
        //执行默认代码块
        break;
}

In the switch statement, when the value of the expression is equal to the value behind a certain case, the code block after the case will be executed. If no case is matched, then Execute the default code block. Each case must be followed by a break statement to jump out of the switch statement.

For example, when we need to output different prompts according to the user's age:

$age = 25;
switch($age){
    case 18:
        echo "你已经成年了";
        break;
    case 25:
        echo "你已经到了适婚年龄";
        break;
    default:
        echo "你还很年轻";
        break;
}

The output result is:

你已经到了适婚年龄

Ternary operator

The ternary operator is a concise branching structure syntax that can select different values ​​based on conditions. The syntax of the ternary operator is as follows:

条件表达式? 表达式1 : 表达式2;

When the conditional expression is true, the value of expression 1 is output, otherwise the value of expression 2 is output.

For example, when we need to output the absolute value of a number:

$a = -5;
echo $a>0 ? $a: -$a;

The output result is:

5

Summary

The program branch structure is a An important programming structure, it can choose different paths according to different conditions to achieve program flexibility and practicality. In the PHP programming language, we can use syntax such as if statements, switch statements, and ternary operators to implement program branch structures. Being proficient in these syntaxes can help us write programs more efficiently.

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