What are the common conditional statements in PHP programming?

PHP is an open source, general-purpose scripting language that is widely used in the field of web development. In PHP programming, conditional statements are one of the indispensable basic syntaxes, used to implement various logical judgments and flow control in the program. This article will introduce common conditional statements in PHP programming.

1. If statement

The most commonly used conditional statement in PHP is the if statement. The syntax of the if statement is as follows:

if (条件表达式) {
    // 条件为真时执行的语句
}

Among them, the conditional expression can be any PHP expression, including constants, variables, arithmetic expressions, etc. If the result of the conditional expression is true, the statement block within the curly braces is executed, otherwise it is not executed.

You can use the elseif keyword to add multiple judgment conditions, as shown below:

if (条件表达式1) {
    // 条件1为真时执行的语句
} elseif (条件表达式2) {
    // 条件2为真时执行的语句
} else {
    // 所有条件都不满足时执行的语句
}

In the if statement, the conditional expression after elseif is only valid if all the previous conditions are not true. It will be judged under the circumstances. If none of the conditions are true, the code in the else block is executed.

2. Switch statement

When there are many conditions that need to be judged, the if statement becomes lengthy and inconvenient to maintain. At this time, you can use the switch statement, which can execute different code blocks based on the value of the expression. The syntax is as follows:

switch (表达式) {
    case 值1:
        // 表达式的值等于值1时执行的语句
        break;
    case 值2:
        // 表达式的值等于值2时执行的语句
        break;
    default:
        // 表达式的值不等于任何一个值时执行的语句
        break;
}

In the switch statement, the value of the expression is compared with the value after each case statement in turn. If the value of the expression is equal to a certain value, the code in the case statement block is executed; if it is not equal to any value, the code in the default statement block is executed.

It should be noted that after the code of each case statement block is executed, a break statement needs to be added to jump out of the switch statement, otherwise the subsequent statement blocks will continue to be executed.

3. Ternary operator

In addition to if statements and switch statements, ternary operators can also be used to implement conditional judgments. The syntax of the ternary operator is as follows:

条件表达式 ? 条件为真时执行的语句 : 条件为假时执行的语句;

The ternary operator contains three parts, namely the conditional expression, the statement executed when the condition is true, and the statement executed when the condition is false. If the result of the conditional expression is true, the statement before ":" is executed, otherwise the statement after ":" is executed.

The ternary operator can be used to simplify code, especially in certain scenarios, such as simple judgment logic or output statements.

To sum up, if statements, switch statements and ternary operators are the most common conditional statements in PHP programming. Using these statements can help us implement various logical controls in the program and improve the readability and maintainability of the program.

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