Q:

Regular expression for email address in Arabic

EDITED
I googled to write a custom regular expression for my web application, and still I can't get what I wanted. 
I want to check if a string passes this pattern or not:
*STRING*STRING INCLUDING ALL CHARS*STRING INCLUDING ALL CHARS#

for example:
*STRING*the first string تست یک*the second string تست دو#

Should return TRUE
*sdsdsd*the first string تست یکthe second string تست دو#

should return FALSE(because it's not the pattern as *STRING*STRING*STRING#)
$check = preg_match("THE RULE", $STRING);

I'm asking for THE RULE here, sorry if I asked my question in a wrong way...

A:

To check if a string has this pattern or not: *STRING*STRING*STRING#:
if (preg_match(
    '/^       # Start of string
    \*        # Match *
    ([^*]*)   # Match any number of characters except *
    \*        # Match *
    ([^*]*)   # Match any number of characters except *
    \*        # Match *
    ([^#]*)   # Match any number of characters except #
    \#        # Match #
    $         # End of string/x', 
    $subject, $matches))

Then use 
filter_var($matches[1], FILTER_VALIDATE_EMAIL)

to check whether the first group might contain an e-mail address.