exit() is a function used in PHP to immediately terminate script execution. Common uses include: 1. Terminate the script in advance when an exception is detected, such as the file does not exist or verification fails; 2. Output intermediate results during debugging and stop execution; 3. Call exit() after redirecting in conjunction with header() to prevent subsequent code execution; In addition, exit() can accept string parameters as output content or integers as status code, and its alias is die().

exit() is a very practical function in PHP, which is used to end the execution of the script immediately. Sometimes you may want to stop subsequent code running when a certain condition is met, such as verification failure, file not exists, or need to return a response in advance.

Below are some common and practical ways to use it to help you better understand how to use it.

Terminate script execution early

The most commonly used scenario is to directly exit the script when some exception is detected to prevent errors from continuing execution.

 if (!file_exists('data.json')) {
    exit('data file does not exist');
}

Like the example above, if the data.json file cannot be found, the script will not continue to run down, but will directly output the prompt message and terminate. This can avoid further serious errors caused by subsequent reading of empty files.

Used to debug output intermediate results

Sometimes when you are debugging, you want to see the value of the current variable, but you don't want the subsequent code to continue running. At this time, you can use exit() to print out the variable and then stop the script:

 echo &#39;<pre class="brush:php;toolbar:false">&#39;;
print_r($user);
exit();

It can also be simplified into one line:

 exit(print_r($user));

This allows you to quickly view the content of $user without being disturbed by the subsequent code. This writing method is very convenient in the early stages of debugging.

Use in conjunction with header redirection

Another common usage is to call exit() ) after jumping in combination with header() to ensure that the page no longer executes other logic after jumping:

 header('Location: login.php');
exit();

If exit() is not added, the subsequent code will theoretically be executed. Although the browser has jumped to the page, the server will still process all the code. Adding exit() can cut off the process more safely.

Pay attention to the small details

• exit() actually has an alias called die() , which has the same function. You can choose which word is more suitable according to the context.
• It can accept a parameter as output content (string) or status code (integral), for example:
  • exit('出錯了') → output text and exit
  • exit(1) → Usually used in command line scripts, indicating an exception exit status

Basically these usages seem to be not complicated, but they are very useful in controlling program flow and debugging.

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