PHP simulates ping command (how to use php exec function)

Use PHP to simulate our commonly used DOS command ping command. What is mainly used here is PHP's built-in function exec to call the system's ping command, thereby realizing the ping command function.

<?php
$to_ping=&#39;www.phpernote.com&#39;;
$count=2;
$psize=66;
echo "正在执行php ping命令，请等待...\n<br><br>";
flush();
while(1){
 echo "<pre class="brush:php;toolbar:false">";
 exec("ping -c $count -s $psize $to_ping", $list);
 for($i=0;$i<count($list);$i++){
  print $list[$i]."\n";
 }
 echo "

"; flush(); sleep(3); } ?>

Note that using the exec function requires the server to support calling system built-in functions. In addition, you can also use PHP built-in functions such as system to achieve this function. The PHP manual explains these two functions:
exec --- Execute external programs
Syntax: string exec ( string command [, array &output [, int & return_var]] )
Description:
exec( ) executes the given command command, However, it does not output anything, it simply returns the last line from the result of the command. If you need to execute a command and get all the data from the command, you can use the passthru() function.
If the parameter array is given, the specified array will be filled with each line output by the command. Note: If the array already contains some elements, exec() will append it to the end of the array. If you If you don't want this function to append elements, you can call unset() before passing the array to exec().
If the parameters array and return_var are given, the status command returned will be written to this variable.
Note: If you allow data from user input to be passed to this function, then you should use escapeshellcmd() to ensure that the user cannot trick the system into executing arbitrary commands.
Note: If you use this function to start a program and want to leave it while executing in the background, you must make sure that the output of the program is redirected to a file or some output data stream. Otherwise PHP will hang until the program execution ends.

system --- Execute an external program and display the output
Syntax: string system (string command [, int &return_var])
Description:
system() executes the given command command and outputs the result. If the parameter return_var is given, the status code of the executed command will be written to this variable.
Note: If you allow data from user input to be passed to this function, then you should use escapeshellcmd() to ensure that the user cannot trick the system into executing arbitrary commands.
Note: If you use this function to start a program and want to leave it while executing in the background, you must make sure that the output of the program is redirected to a file or some output data stream. Otherwise PHP will hang until the program execution ends.
Both of these are used to call system shell commands. The difference is:
exec can return all execution results to the $output function (array), $status is the status of the execution. 0 means success and 1 means failure.
systerm does not need Provide $output function, which returns the result directly. Similarly, $return_var is the status code of execution. 0 is success and 1 is failure. exec example:

<?php  
$a = exec("dir",$out,$status);  
print_r($a);  
print_r($out);  
print_r($status);  
?>

system example:

<?php  
$a = system("dir",$out);  
print_r($a);  
print_r($out);  
?>

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