Usage scenarios and examples of else keyword in PHP

The else keyword in PHP is an important part of the conditional statement. It is usually used in conjunction with the if statement to handle the situation when the condition of the if statement is not true. In this article, we will explore usage scenarios of else keyword and provide some examples.

In program development, we often encounter situations where we need to execute different code blocks based on certain conditions. At this time, you can use the if statement to implement conditional judgment. The basic form of the if statement is as follows:

if (条件){
    // 条件成立时执行的代码
}

However, in actual situations, it is often necessary to deal with situations when the conditions are not true. At this time, you can use the else keyword to write a code block when the condition is not true. The basic form of the else statement is as follows:

if (条件){
    // 条件成立时执行的代码
} else {
    // 条件不成立时执行的代码
}

Next, we will introduce some common usage scenarios and examples to help readers better understand the use of the else keyword.

The first scenario is to determine the parity of a number. By using the if-else statement, we can easily determine whether a number is odd. The sample code is as follows:

$num = 9;

if ($num % 2 == 0) {
    echo "偶数";
} else {
    echo "奇数";
}

In the above code, first determine whether the remainder of $num divided by 2 is 0. If it is true, it means that $num is an even number, otherwise it is an odd number.

The second scenario is to determine whether a number is within a certain range. Suppose we need to determine whether a student's grade is passing. The standard for passing grade is 60 points or more. The sample code is as follows:

$score = 75;

if ($score >= 60) {
    echo "及格";
} else {
    echo "不及格";
}

In the above code, if $score is greater than or equal to 60, "pass" is output; otherwise, "fail" is output.

The third scenario is multi-condition judgment. In some cases, we need to make judgments based on multiple conditions. In this case, we can use multiple if-elseif-else statements to achieve this. The sample code is as follows:

$num = 10;

if ($num > 0) {
    echo "正数";
} elseif ($num < 0) {
    echo "负数";
} else {
    echo "零";
}

In the above code, first determine whether $num is greater than 0, and if true, output "positive number"; if not true, determine whether $num is less than 0, and if true, output " Negative"; if neither condition is true, "zero" is output.

In actual development, the else keyword is used in a wide range of scenarios. In addition to the scenarios in the above examples, it can also be used in various situations such as loop statements and function calls.

To sum up, the else keyword is an important grammatical structure in PHP used to handle when the if condition is not true. It can be used with if statements to execute corresponding code blocks based on different conditions. By rationally using the else keyword, we can more flexibly control the logical flow of the program. I hope readers will have a deeper understanding of the use of the else keyword through the introduction of this article.

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