Loop statement for beginners to PHP

for loop

##Format: for($i=0;$i<10;$i++){

Execute code

}

Now make a case of the sum of 1+2+....10

<?php
	header("Content-type: text/html; charset=utf-8");//设置编码
	//计算1到10之和
	$sum = 0 ;        //定义一个变量  初始值为0
	for($i=1;$i<=10;$i++){      //进入循环，当$i是1时，满足条件，执行$i++
		$sum = $sum + $i;   
	}
	echo $sum;
?>

while loop

Format: while (condition){

Execution code;

}

Use the while loop to calculate the number between 1 and 10 And

<?php
	//while   循环    1到10  之和
	$sum = 0;
	$i = 1;
	while($i<=10){
		$sum = $sum + $i;
		$i++;  //如果没有$i++  那么$i的值就不会发生变化，这样就会一直循环
	}
	echo $sum;
?>

do....while loop

##Format: do{

Execution statement;

}while(condition);

Use do....while to realize the sum of 1 to 10

<?php
	//do......while 循环  写出1到10 之和
	$sum = 0 ;
	$i = 1;
	
	do{
		$sum = $sum +$i;
		$i++;
	}while($i<=10);

	echo $sum;
?>

Note:

No matter whether $i meets the condition or not , the loop body will be executed once. When i = 10, enter the loop body and execute $i++. At this time, the value of $i is 11 and then enter the conditional judgment. If the condition is not met, jump out of the loop

for break and continue statements in the loop

<?php
	//for  循环中break 与continue  的区别
	//当使用break的时候，$i的值是5的时候就跳出循环体
	//使用continue的时候，只有$i是5的时候跳出循环
	for ($i=1;$i<=10;$i++){ 

		if($i==5){
			break;
			//continue;
		}
		echo $i."</br>";
	}
?>

foreach loop (emphasis)

The foreach loop is used to traverse the array.

Format: foreach($array as $value){

Execution code;

}

<?php
	//foreach   循环
	$arr = array('one','two','three','four','five');   //创建一个数组，里面有5个元素
	
	foreach ($arr as $val) {
		echo $val."</br>";
	}
?>

Note: Each cycle is performed. The values ​​in the array will be assigned to the $val variable (the array pointer will move one by one). When you perform the next loop, you will see the next value in the array