Use PHP to implement PHP script engine built-in functions again

// It's really boring. It's a strange idea. I want to re-use PHP to implement some encapsulated functions in PHP,
// The following code mainly implements some string processing functions in PHP, and implements some PHP
// None, but the same function of string processing functions can also be implemented in other languages.
// Now, such as using C/VBScript/Perl, you can have your own function library.
// The following functions may not be able to run successfully, just for learning.
//
// If there is no special statement, it is all because heiyeluren is original. Please keep the author information if you want to use any function.


// {Strlen ()
/**
* Count string length
*
* @ Param string $ str need count length string variable
* @ Return int return count result
*/
Function strlen1 ($ str)
{
If ($ str = '')
Return 0;

$ Count = 0;
While (1)
{
If ($ str [$ count]! = NULL)
{
$ Count;
Continue;
}
Else
Break;
}
Return $ count;
}
//}}}


// {Substr ()
/**
* Get sub string
*
* @ Param string $ str need get sub string variable
* @ Param int $ start get sub string
* @ Param int $ length need get string length
* @ Return string return sub string
*/
Function substr1 ($ str, $ start, $ length = 0)
{
If ($ str = '')
Return;
If ($ start> strlen ($ str ))
Return;
If ($ length! = NULL) & ($ start> 0) & ($ length> strlen ($ str)-$ start ))
Return;
If ($ length! = NULL) & ($ start <0) & ($ length> strlen ($ str) $ start ))
Return;

If ($ length = NULL)
$ Length = (strlen ($ str)-$ start );

If ($ start <0)
{
For ($ I = (strlen ($ str) $ start); $ I <(strlen ($ str) $ start $ length); $ I)
{
$ Substr. = $ str [$ I];
}
}

If ($ length> 0)
{
For ($ I = $ start; $ I <($ start $ length); $ I)
{
$ Substr. = $ str [$ I];
}
}

If ($ length <0)
{
For ($ I = $ start; $ I <(strlen ($ str) $ length); $ I)