What does system mean in php?

The system function in php is used to execute external programs and display output. Its usage syntax is such as "system(string $command, int &$return_var = ?):string". This function executes the command specified by the command parameter. command, and output the execution results.

The operating environment of this article: Windows 7 system, PHP version 7.1, Dell G3 computer.

What does system mean in php?

system (PHP 4, PHP 5, PHP 7, PHP 8)

system — Execute an external program and display the output

Description

system(string $command, int &$return_var = ?): string

Same as the C version of the system() function, this function executes the command specified by the command parameter and outputs the execution result.

If PHP is running in the server module, the system() function will also try to automatically refresh the web server's output cache after each line of output.

If you want to get the raw output of a command without any processing, please use the passthru() function.

Parameters

command

The command to be executed.

return_var

If the return_var parameter is provided, the return status after the external command is executed will be set to this variable.

Return value

Returns the last line of the command output if successful, false if failed

Example system() routine

<?php
echo &#39;<pre class="brush:php;toolbar:false">&#39;;
// 输出 shell 命令 "ls" 的返回结果
// 并且将输出的最后一样内容返回到 $last_line。
// 将命令的返回值保存到 $retval。
$last_line = system(&#39;ls&#39;, $retval);
// 打印更多信息
echo &#39;

---

Last line of the output: ' . $last_line . '

---

Return value: ' . $retval; ?>

Comments

When passing user-provided data to this function, escapeshellarg() or escapeshellcmd() should be used to prevent the user from tricking the system into executing arbitrary commands.

Note:

If a program is started using this function, in order to keep running in the background, the program must redirect output to a file or other output stream. Failure to do so will cause PHP to hang until program execution ends.

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