How to prevent php code from executing downwards

In PHP, you can use the die() and exit() functions to prevent the code from executing downwards. The syntax is "die(message)" and "exit(status)"; the parameters "message" and "status" " is used to specify the message or status number to be written before exiting the script and cannot be omitted.

The operating environment of this tutorial: windows7 system, PHP7.1 version, DELL G3 computer

Let the php code not Method of downward execution:

When die() and exit() are called in a script, the entire script will be terminated. They can all be used to prevent a script from continuing to execute, so that certain important operations don't happen.

1.die()

phpdie is a function used to output a message and exit the current script. Its syntax is "die(message)", and the parameter "message" is specified when exiting the script. The message or status number was previously written, and the status number is not written to the output.

Output a message and exit the current script:

<?php
$site = "http://www.php.cn/";
fopen($site,"r")
or die("Unable to connect to $site");
?>

2. exit()

The function of phpexit is to output a message and exit the current script. The exit function is die () function alias, its usage syntax is "exit(status)", the parameter status specifies the message or status number written before exiting the script.

If status is a string, the function will output the string before exiting.

If status is an integer, this value will be used as the exit status. The exit status has a value between 0 and 254. Exit status 255 is reserved by PHP and will not be used. Status 0 is used to terminate the program successfully.

<?php
$site = "http://www.php.cn/";
fopen($site,"r")
or exit("Unable to connect to $site");
?>

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