How to force a PHP command line script to run a single process

This article describes a function that forces PHP to execute in a single process. it is mostly used in php command lines and some special requirements. For more information, see The code is as follows:
/**
* Single process guarantee
*
* @ Param string $ processName process name
* @ Param string $ pidFile process file path
* @ Return boolean whether to continue executing the current process
*/
Function singleProcess ($ processName, $ pidFile)
{
If (file_exists ($ pidFile) & $ fp = @ fopen ($ pidFile, "rb "))
{
Flock ($ fp, LOCK_SH );
$ Last_pid = fread ($ fp, filesize ($ pidFile ));
Fclose ($ fp );

If (! Empty ($ last_pid ))
{
$ Command = exec ("/bin/ps-p $ last_pid-o command = ");

If ($ command = $ processName)
{
Return false;
}
}
}

$ Cur_pid = posix_getpid ();

If ($ fp = @ fopen ($ pidFile, "wb "))
{
Fputs ($ fp, $ cur_pid );
Ftruncate ($ fp, strlen ($ cur_pid ));
Fclose ($ fp );

Return true;
}
Else
{
Return false;
}
}

/**
* Get the Command corresponding to the current process
*
* @ Return string command and its parameters
*/
Function getCurrentCommand ()
{
$ Pid = posix_getpid ();
$ Command = exec ("/bin/ps-p $ pid-o command = ");

Return $ command;
}

Usage:
The code is as follows:
If (singleProcess (getCurrentCommand (), 'path/to/script. pid '))
{
// Code goes here
}
Else
{
Exit ("Sorry, this script file has already been running... \ n ");
}