How to exit the script program using PHP functions

In the previous article "How to use PHP functions to convert decimal numbers", we learned how to use PHP to convert binary numbers and decimal numbers, decimal numbers and hexadecimal numbers. Interested friends can learn about the mutual conversion of decimal numbers and octal numbers. The focus of this article is "terminate the running of the script and exit the current program"; we need to tell PHP through a statement Engine, other statements after this statement do not need to be executed.

So how can we terminate script execution? In fact, PHP provides two

built-in functions "

die()" and "exit()" to complete this operation! Let’s take a look at the following two examples

<?php
$a = 1;
$b = 9;
echo $a; // 输出 1
die(); // 终止脚本运行，下面不在运行
$sum = $a + $b;
echo $sum; // 不被输出
?>

Output results:

<?php
$a = 1;
$b = 9;
echo $a; // 输出 1
exit(); // 终止脚本运行，下面不在运行
$sum = $a + $b;
echo $sum; // 不被输出
?>

Output results:

It can be seen that both programs exit (terminate execution) on line 5, and the code on lines 6 and 7 is not executed.

In fact, the two names exit and die point to the same function. die() is an alias of the exit() function. The two functions are essentially the same. And the die() and exit() functions also accept an optional parameter

$message

, which is used to output a message when exiting the current script. <pre class="brush:php;toolbar:false">exit($message); die($message);</pre>$message can be a specific value (int type) or a string (String type), or you can enter no parameters.

If it is of type int, the value will be used as the exit status code and will not be printed. (Exit status codes range from 0 to 254.)

• <?php
  $a = 1;
  $b = 9;
  echo $a; // 输出 1
  exit(0); // 终止脚本运行，下面不在运行
  $sum = $a + $b;
  echo $sum; // 不被输出
  ?>

Note: Do not use the exit status code 255, which is reserved by PHP. Status code 0 is used to terminate the program successfully.

If it is a String type, the function will print the string and exit the current script;

• <?php
  header("content-type:text/html;charset=utf-8");
  $a = 1;
  $b = 9;
  echo $a; // 输出 1
  exit("<br>退出脚本"); // 终止脚本运行，下面不在运行
  $sum = $a + $b;
  echo $sum; // 不被输出
  ?>

Using this feature, when the program errors, we can pass it a string, which will be output as it is on the system terminal

$fp=fopen("./readme.txt","r") or die("不能打开该文件");
//这种情况下，如果fopen函数被调用返回布尔值false时，die()将立即终止脚本，并马上打印
//传递给它的字符串，“死前还能说一两句话”。

Note: Although die() and exit() Both are the same, but there are subtle selectivity in their common use. For example:

When the value passed to the exit and die functions is 0, it means that the execution of the script is terminated early, usually using the name exit().

When the program errors, you can pass it a string, which will be output as it is on the system terminal, usually using the name die().

die() and exit() functions can be used in loop statements to break out of the loop

<?php
    for ($i=0; $i < 10; $i++) {
        if ($i == 2) {
            die;
        } else {
            echo &#39;$i = &#39;.$i.&#39;<br>&#39;;
        }
    }
    echo &#39;循环外的一个输出<br>&#39;;
?>

Output result:

In addition to using the die() and exit() functions, you can also use the

return statement to terminate the program. First we need to know:

return is a language structure rather than a function

. return: Indicates exiting at this point; if it is in a function, it means exiting the function; if it is in a script, it means the script stops executing.

If called in the global scope, the current script file aborts running. If the current script file is included or required, control is returned to the calling file. In addition, if the current script is included, the return value will be regarded as the return value of the include call, and accordingly a variable is defined in the main script file to receive the return value.

• <?php
  //包含demo13_ stop. php
  $test = include &#39; demo13_ stop.php&#39; ;
  var_ dump($test) ;
  ?>

demo13_stop.php

<?php
   //终止脚本执行
   echo &#39;start&#39;;

   //return
   return &#39;*&#39;;
?>

If return is called in the main script file, the script stops running.

Summary:

PHP provides three ways to terminate script execution: return, die(), exit()

return is generally used to end the execution of the current function/file/script/other, and return information to other functions/files/scripts/others that called it.

die() and exit() stop the current execution here and no longer proceed. If there are parameters, they will be printed directly (only for strings).

Then if what you need to output is a numerical variable, you can use

"{}"

to wrap the numerical variable: <pre class="brush:php;toolbar:false">&lt;?php $a = 1; $b = 9; exit(&quot;{$a}&quot;); // 终止脚本运行，下面不在运行 $sum = $a + $b; echo $sum; // 不被输出 ?&gt;</pre>The output result is:

1

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