diff --git a/languages/php.php b/languages/php.php
index e1d9054..84bb1db 100644
--- a/languages/php.php
+++ b/languages/php.php
@@ -331,7 +331,6 @@ abstract class AbstractClassName
 
 }
 
-
 /**
  * Basic Implementation of LoggerAwareInterface.
  * @see https://github.com/php-fig/log/blob/master/Psr/Log/LoggerAwareTrait.php
@@ -366,3 +365,106 @@ class ClassWithLogger
      */
     use LoggerAwareTrait;
 }
+
+
+/**
+ * PHP Regex.
+ */
+
+// Meta Characters.
+
+^   Start of subject (or line in multiline mode)
+$   End of subject (or line in multiline mode)
+[   Start character class definition
+]   End character class definition
+|   Alternates, eg (a|b) matches a or b
+(   Start subpattern
+)   End subpattern
+\   Escape character
+
+// Pattern Modifiers.
+
+i   Caseless - ignore case
+m   Multiline mode - ^ and $ match start and end of lines
+s   Dotall - . class includes newline
+x   Extended- comments & whitespace
+e   preg_replace only - enables evaluation of replacement as PHP code
+S   Extra analysis of pattern
+U   Pattern is ungreedy
+u   Pattern is treated as UTF-8
+
+// Subpattern Modifiers & Assertions.
+(?:)    Non capturing subpattern    ((?:foo|fu)bar) matches foobar or fubar without foo or fu appearing as a captured subpattern
+(?=)    Positive look ahead assertion   foo(?=bar) matches foo when followed by bar
+(?!)    Negative look ahead assertion   foo(?!bar) matches foo when not followed by bar
+(?<=)   Positive look behind assertion  (?<=foo)bar matches bar when preceded by foo
+(?<!)   Negative look behind assertion  (?<!foo)bar matches bar when not preceded by foo
+(?>)    Once-only subpatterns   (?>\d+)bar Performance enhancing when bar not present
+(?(x))  Conditional subpatterns (?(3)foo|fu)bar Matches foo if 3rd subpattern has matched, fu if not
+(?#)    Comment (?# Pattern does x y or z)
+
+// Base Character Classes
+\w  Any "word" character (a-z 0-9 _)
+\W  Any non "word" character
+\s  Whitespace (space, tab CRLF)
+\S  Any non whitepsace character
+\d  Digits (0-9)
+\D  Any non digit character
+.   (Period) - Any character except newline
+
+// Multiplicity.
+n*  Zero or more of n
+n+  One or more of n
+n?  Zero or one occurrences of n
+{n} n occurrences exactly
+{n,}    At least n occurrences
+{,m}    At most m occurrences
+{n,m}   Between n and m occurrences (inclusive)
+
+
+// PHP Regular Expression Functions.
+
+Function    Description
+preg_match()    The preg_match() function searches string for pattern, returning true if pattern exists, and false otherwise.
+preg_match_all()    The preg_match_all() function matches all occurrences of pattern in string. Useful for search and replace.
+preg_replace()  The preg_replace() function operates just like ereg_replace(), except that regular expressions can be used in the pattern and replacement input parameters.
+preg_split()    Preg Split (preg_split()) operates exactly like the split() function, except that regular expressions are accepted as input parameters.
+preg_grep() The preg_grep() function searches all elements of input_array, returning all elements matching the regex pattern within a string.
+preg_ quote()   Quote regular expression characters
+
+// Code Snippets.
+
+//A better solution for validate email syntax is using filter_var.
+if (filter_var('test+email@fexample.com', FILTER_VALIDATE_EMAIL)) {
+    echo "Your email is ok.";
+} else {
+    echo "Wrong email address format.";
+}
+
+//Validate username, consist of alpha-numeric (a-z, A-Z, 0-9), underscores, and has minimum 5 character and maximum 20 character.
+//You could change the minimum character and maximum character to any number you like.
+$username = "user_name12";
+if (preg_match('/^[a-z\d_]{5,20}$/i', $username)) {
+    echo "Your username is ok.";
+} else {
+    echo "Wrong username format.";
+}
+
+//Validate domain
+$url = "http://domain-name.com/";
+if (preg_match('/^(http|https|ftp):\/\/([A-Z0-9][A-Z0-9_-]*(?:\.[A-Z0-9][A-Z0-9_-]*)+):?(\d+)?\/?/i', $url)) {
+    echo "Your url is ok.";
+} else {
+    echo "Wrong url.";
+}
+
+//Extract domain name from certain URL
+$url = "http://domain-name.com/index.html";
+preg_match('@^(?:http://)?([^/]+)@i', $url, $matches);
+$host = $matches[1];
+echo $host; // domain-name.com
+
+//Highlight a word in the content
+$text = "A regular expression (shortened as regex) is a sequence of characters that define a search pattern. Usually such patterns are used by string-searching algorithms for 'find' or 'find and replace' operations on strings, or for input validation.";
+$text = preg_replace("/\b(regex)\b/i", 'replaced content', $text);
+echo $text; /*A regular expression (shortened as replaced content) is a sequence of characters that define a search pattern. Usually such patterns are used by string-searching algorithms for 'find' or 'find and replace' operations on strings, or for input validation.*/