Dynamic Web technology PHP program string processing function

?
//------------------------
PHP Built-in string function implementation
//------------------------

String length
function strlen ($STR)
{
if ($str = = ") return 0;
$count = 0;
while (1) {
if ($str [$count]!= NULL) {
$count + +;
Continue
}else{
Break
}
}
return $count;
}

To intercept a child string
function substr ($str, $start, $length =null)
{
if ($str = = ' | | $start >strlen ($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 + +) {
$substr. = $str [$i];
}
}
return $substr;
}

String Flip
function Strrev ($STR)
{
if ($str = = ") return 0;
for ($i = (strlen ($str)-1); $i >=0; $i-) {
$rev _str. = $str [$i];
}
return $rev _str;
}

String comparisons
function strcmp ($s 1, $s 2)
{
if (strlen ($s 1) < strlen ($s 2)) return-1;
if (strlen ($s 1) > strlen ($s 2)) return 1;
For ($i =0 $i <strlen ($s 1); $i + +) {
if ($s 1[$i] = = $s 2[$i]) {
Continue
}else{
return false;
}
}
return 0;
}

Find string
function Strstr ($STR, $SUBSTR)
{
$m = strlen ($STR);
$n = strlen ($SUBSTR);
if ($m < $n) return false;
For ($i =0 $i <= ($m-$n + 1); $i + +) {
$sub = substr ($str, $i, $n);
if (strcmp ($sub, $substr) = = 0) return $i;
}
return false;
}

String substitution
function Str_replace ($substr, $newsubstr, $STR)
{
$m = strlen ($STR);
$n = strlen ($SUBSTR);
$x = strlen ($NEWSUBSTR);
if (STRCHR ($str, $substr) = = false) return false;
For ($i =0 $i <= ($m-$n + 1); $i + +) {
$i = STRCHR ($str, $SUBSTR);
$str = Str_delete ($str, $i, $n);
$str = Str_insert ($str, $i, $NEWSTR);
}
return $str;
}
?>

<?php
//--------------------
Self-Implementation String handler function
//--------------------

Insert a section of string
function Str_insert ($str, $i, $SUBSTR)
{
for ($j =0; $j < $i; $j + +) {
$startstr. = $str [$j];
}
for ($j = $i; $j <strlen ($STR); $j + +) {
$laststr. = $str [$j];
}
$str = ($startstr. $substr. $laststr);
return $str;
}

//delete a section of string
function Str_delete ($str, $i, $j)
{
        for ($c =0; $c &L t; $i;  $c + +) {
                 $STARTSTR. = $str [$c];
       }
        for ($c = ($i + $j); $c <strlen ($STR); $c + +) {
                 $laststr  . = $str [$c];
       }
         $str = ($startstr. $laststr);
        return $str;
}

Copy string
function strcpy ($s 1, $s 2)
{
if (strlen ($s 1) ==null | |!isset ($s 2)) return;
for ($i =0; $i <strlen ($s 1); $i + +) {
$s 2[] = $s 1 [$i];
}
return $s 2;
}

Connection string
function strcat ($s 1, $s 2)
{
if (!isset ($s 1) | | |!isset ($s 2)) return;
$newstr = $s 1;
for ($i =0; $i <count ($s); $i + +) {
$newstr. = $st [$i];
}
return $newsstr;
}

Simple encoding function (corresponding to the Php_decode function)
function Php_encode ($STR)
{
if ($str = = ' && strlen ($STR) >128) return false;
for ($i =0; $i <strlen ($STR); $i + +) {
$c = Ord ($str [$i]);
if ($c >31 && $c <107) $c + + 20;
if ($c >106 && $c <127) $c-= 75;
$word = Chr ($c);
$s. = $word;
}
return $s;
}

Simple decoding function (corresponding to the Php_encode function)
function Php_decode ($STR)
{
if ($str = = ' && strlen ($STR) >128) return false;
for ($i =0; $i <strlen ($STR); $i + +) {
$c = Ord ($word);
if ($c >106 && $c <127) $c = $c-20;
if ($c >31 && $c <) $c = $c +75;
$word = Chr ($c);
$s. = $word;
}
return $s;
}

Simple cryptographic functions (corresponding to the Php_decrypt function)
function Php_encrypt ($STR)
{
$encrypt _key = ' abcdefghijklmnopqrstuvwxyz1234567890 ';
$decrypt _key = ' ngzqtcobmuhelkpdawxfyivrsj2468021359 ';
if (strlen ($str) = = 0) return false;
for ($i = 0; $i <strlen ($STR); $i + +) {
For ($j =0 $j <strlen ($encrypt _key); $j + +) {
if ($str [$i] = = $encrypt _key [$j]) {
$enstr. = $decrypt _key[$j];
Break
}
}
}
return $enstr;
}

Simple decryption function (corresponding to the Php_encrypt function)
function Php_decrypt ($STR)
{
$encrypt _key = ' abcdefghijklmnopqrstuvwxyz1234567890 ';
$decrypt _key = ' ngzqtcobmuhelkpdawxfyivrsj2468021359 ';
if (strlen ($str) = = 0) return false;
for ($i = 0; $i <strlen ($STR); $i + +) {
For ($j =0 $j <strlen ($decrypt _key); $j + +) {
if ($str [$i] = = $decrypt _key [$j]) {
$enstr. = $encrypt _key[$j];
Break
}
}
}
return $enstr;
}
?>