What is the usage of break in php

In PHP, break is used to jump out of the current syntax structure and execute the following statement; it can be used in statements such as switch, for, while, and do while to terminate the code of the loop body and immediately jump out of the current statement. Loop, execute the code after the loop. The break statement can take a parameter n, which represents the number of levels to jump out of the loop. If you want to jump out of multiple loops, you can use n to represent the number of levels to jump out of. If there is no parameter, the default is to jump out of the current loop.

The operating environment of this tutorial: windows7 system, PHP8 version, DELL G3 computer

The loop structure in PHP generally includes for loop and while loop , do{} while loop and foreach loop. No matter which kind of loop, there are roughly several ways to jump out of the loop in PHP:

<?php
 
$i = 1;
while (true) { // 这里看上去这个循环会一直执行
    if ($i==2){// 2跳过不显示
       $i++;
       continue;
    } else if($i==5) {// 但到这里$i=5就跳出循循环了
       break;
    } else{
       echo $i . &#39;<br>&#39;;
    }
    $i++;
}
exit;
 
echo&#39;这里不输出&#39;;
?>

Result:

1
3
4

break keyword

The break keyword can make the program jump out of the current loop. It can be used in statements such as switch, for, while and do while, which can terminate the code of the loop body. And immediately jump out of the current loop and execute the code after the loop.

The function of break is to jump out of the current syntax structure and execute the following statement. The break statement can take a parameter n, which represents the number of levels to jump out of the loop. If you want to jump out of multiple loops, you can use n to represent the number of levels to jump out of. If there is no parameter, the default is to jump out of the current loop.

The execution flow of the break keyword is shown in the figure below:

[Example]

<?php
for ($i=0; $i < 10; $i++) {
    if($i == 3) {
        break;
    }
    echo $i;
}
?>

In the for loop, determine the current $ The loop is terminated when the value of i is 3. The execution result of the code is:

012

The effect is the same in the while, do while and foreach loop statements. The function of the break statement is to terminate the loop.

Explanation:

The break statement can not only jump out of the current loop, but also specify how many levels of loops to jump out of. The syntax format is:

break n;

The parameter n specifies the number of loop levels to jump out of

Example:

<?php
    while (true) {
        for (;;) {
            for ($i=0; $i < 10; $i++) {
                echo &#39;$i = &#39;.$i.&#39;, <br>&#39;;
                if($i == 3) {
                    echo &#39;变量 $i 等于 3，跳出第一层循环。<br>&#39;;
                    break 1;
                }
            }
            for ($j=0; $j < 10; $j++) {
                echo &#39;$j = &#39;.$j.&#39;, <br>&#39;;
                if($j == 4) {
                    echo &#39;变量 $j 等于 4，跳出最外层循环。&#39;;
                    break 3;
                }
            }
        }
        echo &#39;由于前面直接跳出了最外层循环，所以这里的打印信息是看不到的！&#39;;
    }
?>

The running results are as follows:

$i = 0,
$i = 1,
$i = 2,
$i = 3,
变量 $i 等于 3，跳出第一层循环。
$j = 0,
$j = 1,
$j = 2,
$j = 3,
$j = 4,

Variable $j is equal to 4, jump out of the outermost loop.

continue keyword

continue is used in a loop structure to control the program to abandon the code after the continue statement of this loop and transfer And proceed to the next cycle. continue itself does not jump out of the loop structure, it just gives up the loop this time. If continue is used in a non-loop structure (such as an if statement, a switch statement), the program will error.

For example, in the following PHP code snippet:

<?php
for($i = 1;$i <= 100; $i++ ){
if($i % 3 == 0 || $i % 7 == 0){
continue;
}
& #160;  else{
echo”$i \n<br/>”;
}
}
?>

The function of the PHP code snippet is to output within 100, which is neither divisible by 7 nor 3 For those natural numbers that are divisible, the if conditional statement is first used in the loop to determine the numbers that can be divisible, and then the continue; statement is executed to directly enter the next loop. The following output statement will not be executed.

goto keyword

goto is actually just an operator. Like other languages, the abuse of goto and the abuse of goto are not encouraged in PHP. It will cause the readability of the program to be seriously reduced. The function of goto is to jump the execution of the program from the current position to any other position. goto itself does not have the function of ending the loop, but its jump position allows it to be used as a jump out of the loop. However, PHP5.3 and above have stopped supporting goto, so you should try to avoid using goto.
The following is an example of using goto to jump out of the loop

for($i = 1000;$i >= 1 ; $i– ){
    if( sqrt($i) <= 29){
        goto a;
    }
    echo “$i”;
}
a:
echo” this is the end”;

The example uses goto to jump out of the loop. This example is used to detect those numbers within 1000 whose square root is greater than 29 .

exit keyword

exit is used to end program execution. It can be used anywhere and has no meaning of jumping out of the loop. exit can take one parameter. If the parameter is a string, PHP will output the string directly. If the parameter is an integer (range is 0-254), that parameter will be used as the end status.

<?php
    for($i = 1000;$i >= 1 ; $i– ){
        if( sqrt($i) >= 29){
            echo”$i \n<br/>”;
        }
        else{
            exit;
        }
    }
    echo”本行将不会被输出”;
?>

In the above example, the execution of the code ends directly in the loop. This will cause the following code to not be executed. If it is in a php web page, even Even the html code after exit will not be output.

return keyword

The return statement is used to end a piece of code and return a parameter. It can be called from a function, or from a file included in an include() or require() statement, or it can be called from the main program. If it is called from a function, the program will end immediately and return the parameters. , if it is called from a file included in the include() or require() statement, program execution will immediately return to the program that called the file, and the return value will be used as the return value of include() or require(). And if it is called in the main program, then the main program will stop executing immediately

<?php
    for($i = 1000;$i >= 1 ; $i– ){
        if( sqrt($i) >= 29){
            echo”$i \n<br/>”;
        }
        else{
           return;
        }
    }
    echo”本行将不会被输出”;
?>

这里的例子和上面使用exit的效果是一样的。

在循环结束条件，自然跳出

这个当然是最好理解了，当循环满足循环临界条件时就是自己退出。

以上是PHP中跳出循环的几种方式的简单总结。

 if不是循环结构，所以不能使用break，continue退出。如果你非要在if语句中这样用的话，可以把这个if语句放在一个循环结构中

$i=0;
$s=1;
while($i==0)
{
        if($s==1)
        {
                $v=8;
                break;
        }
        $v=9;
}

echo $v;

推荐学习：《PHP视频教程》

The above is the detailed content of What is the usage of break in php. For more information, please follow other related articles on the PHP Chinese website!