The difference between PHP functions and Shell functions

The main differences between PHP functions and Shell functions are security (PHP functions are more secure), reliability (Shell functions vary depending on the operating system), functionality (Shell functions are more powerful but limited by the shell), performance (PHP functions are usually faster) and complexity (Shell functions are more complex). They are both used for file system, process and command operations, but PHP functions are built-in while Shell functions are called through an external shell. Therefore, in server file download scenarios, the file_put_contents() function is more secure, while the wget command is more flexible.

The difference between PHP functions and Shell functions

Introduction

PHP functions and Shell functions are tools used to deal with file systems, processes, and commands. However, there are some key differences between them that are important to understand in order to use PHP scripts effectively.

PHP Functions

PHP functions are built into the PHP language. They provide a secure way to access system resources and provide reliable behavior across different operating systems. PHP functions typically use PHP file system functions, process control functions, and command execution functions.

Example:

// 获取当前目录
$current_dir = getcwd();

// 创建一个新目录
mkdir("new_directory");

// 执行命令
exec("ls -l");

Shell function

Shell function is called by calling an external shell (such as Bash, Zsh or Cmd) to execute. They provide a more powerful way to interact with the system, but they may also be less secure depending on the behavior of the underlying shell. PHP supports calling shell functions through the shell_exec() and exec() functions.

Example:

// 获取当前目录
$current_dir = shell_exec('pwd');

// 创建一个新目录
shell_exec('mkdir new_directory');

// 执行命令
$output = exec('ls -l');

Difference summary

Features	PHP Function	Shell Function
Security	More secure	Possibly unsafe
Reliability	Reliable	May vary by operating system
Function	File system, process control, command execution	More powerful functions, but may be limited by shell
Performance	Usually faster	May be slower depending on shell
Complex Sex	Relatively simple	may be more complex, you need to understand the underlying shell

Practical case

Suppose you need to download a file from the server. You can use PHP's file_put_contents() function:

file_put_contents('file.txt', file_get_contents('http://example.com/file.txt'));

Alternatively, you can use the shell's wget command:

exec('wget http://example.com/file.txt');

In terms of security , file_put_contents() function is safer because it does not call external programs and PHP handles all errors. However, the wget command is more flexible as it can be configured using command line options.

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