Usage and examples of exit keyword in PHP

Usage and examples of the exit keyword in PHP

In PHP programming, we often use the exit keyword to terminate the execution of the program. The function of the exit keyword is to immediately terminate the execution of the current script and return a specified value (default is 0). This article will introduce the specific usage of the exit keyword and provide some examples for readers' reference.

Usage 1: Simple exit

The simplest usage is to just use exit without passing any parameters. This immediately terminates the execution of the script and returns 0. For example:

echo "This line of code will be executed.";
exit;
echo "This line of code will not be executed.";
? >

In the above example, the echo statement in the first line will be executed, but because it exits immediately after the exit keyword, the echo statement in the second line will not be executed.

Usage 2: Specify the exit status

The exit keyword can also accept an integer parameter to specify the exit status. Generally, an exit status of 0 indicates that the program ended normally, while a non-zero exit status indicates that an error occurred during program execution. For example:

echo "This line of code will be executed.";
exit(1);
echo "This line of code will not be executed.";
?>

In the above example, exit(1) specifies the exit status as 1. When the program executes the exit keyword, the script will terminate immediately and return exit status 1.

Usage 3: Combined with conditional statements

We can also use the exit keyword in combination with conditional statements to decide whether to exit the program based on specific conditions. For example:

$score = 85;

if ($score < 60) {
echo "Failed!";
exit;
}

echo "Pass!";
?>

In the above example, if the score $score is less than 60, it will output "Fail!" and exit program; otherwise, "Pass!" will be output.

Usage 4: Terminate the execution of the included file

In PHP, we can use the include or require keywords to include external files into the current script. If we want to terminate the program immediately if a problem occurs during the execution of the included file, we can use the exit keyword. For example:

File example.php:

echo "This is the code in the include file.";
exit;
?>

File test.php:

echo "This is the code in the main file.";
include "example.php";
echo " This line of code will not be executed.";
?>

In the above example, when the test.php file is executed to include "example.php", the echo statement in example.php will is executed, but because the exit keyword is used in example.php to terminate the program, the subsequent code in test.php "This line of code will not be executed." will not be executed.

Summary

The exit keyword is often used in PHP to terminate the execution of the program and return a specified exit status. It can be used in different scenarios, such as simple code exit, specifying exit status, combining conditional statements to decide whether to exit, terminating the execution of included files, etc. When using the exit keyword, we should choose the usage reasonably according to actual needs, and ensure that it is used to terminate the execution of the program at the appropriate time.

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