What is a do...while loop? Is it different from while loop? (with code)

The previous article introduced you to "Detailed Introduction - Loop Statement". This article continues to introduce to you what is a do...while loop? And the difference with while loop? Don’t hesitate to come in and learn! You will definitely gain something! ! !

do...while loop:

Format:

do{

Loop body

[Conditions for self-increment or self-decrement]

}while (conditional expression);

Analysis: For self-increment and self-decrement, it is optional (you can write it or not, we generally use square brackets to indicate whether it can be written or not). For Boolean type conditional loops, there is no need to write it.

We explain the specific structure by code operation. The code is as follows:

<?php 
/******do...while 循环  循环格式1******/
//1.初始化一个变量
 $num = 10;
 do{
     echo $num.&#39;&#39;;
     //每次循环执行完毕后，条件变量进行改变
     $num --;
 }while($num>0);
?>

The running results are as follows:

Code analysis:

For do...while loop, it is also called Boolean value loop

If the expression in while() is true, it will be executed. The expression in the loop body {} is called a loop. Body

If it is false, stop the loop

We define an initial variable, the loop starts from 1-10, enter the do loop, output a value and assign it to $num--, thereby getting a The new value is used to determine whether the while condition is true. If it is true, execution will continue, otherwise execution will stop.

Example 2:

<?php 
/******do...while 循环  循环格式1******/
/*
   while循环叫做布尔值循环
   while（）内的表达式如果为真则执行循环体{}内的就叫做循环体
   如果为假，停止循环
*/
//1.初始化一个变量
 $num = 10;
 do{
     echo $num.&#39;&#39;;
     //每次循环执行完毕后，条件变量进行改变
     $num --;
 }while($num>0);
 echo &#39;<hr/>&#39;;
//循环
$num = 1;
do{
    if($num < 10){
        echo &#39;0&#39;.$num.&#39;&#39;;
    }else{
        echo $num.&#39;&#39;;
    }
    //判断10的倍数换行
    if($num % 10 == 0){
        echo &#39;<br/>&#39;;
    }
    $num ++;
}while($num <= 50);
?>

The running results are as shown in the figure:

Code analysis:

First, initialize a variable, enter the do loop, and then output its value. The output value enters the if statement to determine whether it is a multiple of 10. If so, perform a newline; add a newline tag（<br>）;

Secondly, we need to know that if we only judge multiples of 10, we only need to align the bottom 4 lines, so we need to add 0 forward and backward to get The above code;

do...The difference between while loop and while loop:

Based on the while learned previously and the learning in today’s article, we can get The difference between while and do...while:

• The execution of each loop body of the while loop must be judged based on the result of the while conditional expression;

• do...while Except for the first time, every execution of the remaining loop must determine whether the while conditional expression is true;

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