Detailed explanation of how to jump out of multiple loop methods in PHP

(1) break

break is used in the various loops and switch statements mentioned above. Its function is to jump out of the current grammatical structure and execute the following statements. The break statement can take a parameter n, indicating the number of levels to jump out of the loop. If you want to jump out of multiple loops, you can use n to indicate the number of levels to jump out of. If there is no parameter, the default is to jump out of the current loop.

Look at the following example of multiple loop nesting:

for($i=1;$i<=10;$i++){    
        for($j=1;$j<=10;$j++){    
            $m=$i * $i + $j * $j;    
            echo $m,"<br/>";    
            if($m<90||$m>190) {    
                break 2;    
            }    
        }    
    }

Break 2 is used here to jump out of the double loop. You can try it out and remove 2. The result will be completely different. of. If no parameters are used, only this loop will be jumped out, and the first level loop will continue to execute.

(2)continue

continue is used in a loop structure to control the program to abandon the code after the continue statement of this loop and move to the next loop. . 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 or a switch statement), the program will error.

For example, in the following PHP code fragment:

for($i=1;$i<=100;$i++){    
        if($i%3==0||$i%7==0){    
            continue;    
        }else{    
            echo $i,"<br/>";    
        }    
    }

(3) return

The return statement is used to end a piece of code and Returns one 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, the main program will stop execution immediately.

The following is a case of using return to exit the loop:

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

The example here has the same effect as using exit.

In the end condition of the loop, it will jump out naturally. This is of course the best to understand. When the loop meets the critical condition of the loop, it will exit by itself.

(4)exit

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 string, PHP will directly output the string. If the parameter is integerinteger (range is 0-254), that parameter will Used as the end state.

The following is a case of using exit to exit the loop:

for($i=1000;$i>=1;$i–){    
        if(sqrt($i)>=29){    
            echo $i,"<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, which will cause the subsequent code to not be executed. If it is in a php web page, even the html code after exit will not be output.

(5)die

The die function exits the loop and exit is the same, so I won’t explain it in detail here.

(6) goto

goto is actually just a operator. Like other languages, the abuse of goto is not encouraged in PHP. Abuse of goto will lead to program corruption. Readability is severely 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 within 1000, the square root of those numbers is greater than 29.

The above is a brief summary of several ways to jump out of loops in PHP.

The above is the detailed content of Detailed explanation of how to jump out of multiple loop methods in PHP. For more information, please follow other related articles on the PHP Chinese website!