Regular Expressions 101

Save & Manage Regex

  • Current Version: 1
  • Save & Share
  • Community Library

Flavor

  • PCRE2 (PHP)
  • ECMAScript (JavaScript)
  • Python
  • Golang
  • Java
  • .NET 7.0 (C#)
  • Rust
  • PCRE (Legacy)
  • Regex Flavor Guide

Function

  • Match
  • Substitution
  • List
  • Unit Tests
Sponsors
An explanation of your regex will be automatically generated as you type.
Detailed match information will be displayed here automatically.
  • All Tokens
  • Common Tokens
  • General Tokens
  • Anchors
  • Meta Sequences
  • Quantifiers
  • Group Constructs
  • Character Classes
  • Flags/Modifiers
  • Substitution
  • A single character of: a, b or c
    [abc]
  • A character except: a, b or c
    [^abc]
  • A character in the range: a-z
    [a-z]
  • A character not in the range: a-z
    [^a-z]
  • A character in the range: a-z or A-Z
    [a-zA-Z]
  • Any single character
    .
  • Alternate - match either a or b
    a|b
  • Any whitespace character
    \s
  • Any non-whitespace character
    \S
  • Any digit
    \d
  • Any non-digit
    \D
  • Any word character
    \w
  • Any non-word character
    \W
  • Non-capturing group
    (?:...)
  • Capturing group
    (...)
  • Zero or one of a
    a?
  • Zero or more of a
    a*
  • One or more of a
    a+
  • Exactly 3 of a
    a{3}
  • 3 or more of a
    a{3,}
  • Between 3 and 6 of a
    a{3,6}
  • Start of string
    ^
  • End of string
    $
  • A word boundary
    \b
  • Non-word boundary
    \B

Regular Expression
Processing...

Test String

Code Generator

Generated Code

$re = '/(?: <\?php (?: [^"\'\/<\?]+ | (?: "(?:[^\\\\"]|\\\\[\s\S])*" | # \'(?:[^\\\\\']|\\\\[\s\S])*\' #| \/\*(?:[^\*]|\*[^\/])*\*\/ | (?:\#|\/\/).+(?:\n|$) | (?: <<<\s* (?: (?:\'([a-zA-Z0-9_]+)\'\s*?\n)(?:[^\n]*\n)*?\s*\1\s*?;?\s*?(?:\n|$) | (?:([a-zA-Z0-9_]+)\s*?\n)(?:[^\n]*\n)*?\s*\2\s*?;?\s*?(?:\n|$) ) ) ) | (?:[^?]|\?[^>]) )* (?:\?>|$) )/xi'; $str = '<!-- The PHP masterpage --> <?php $matches = array(); // separates $re = <<<PREG /^ (?:\\\\s*(?:<!--.*?-->))* <\\\\?php\\\\s*include\\\\s*(\\\\()?\\\\s*([\\\\\'\\\\"])(?:(?!\\\\2).)*(?-i)Master\\\\.php(?i)\\\\2(?(-2)\\\\))\\\\s*;\\\\s*\\\\?>\\\\s* (?:\\\\s*(?:<!--.*?-->))* <master\\\\s*src=([\\\\\'\\\\\\"])(?<master_url>.+?)\\\\3\\\\/>(?<content>[\\s\\S]*) $ /ix PREG; $re = <<<PREG2 /^ (?:\\\\s*(?:<!--.*?-->))* <\\\\?php\\\\s*include\\\\s*(\\\\()?\\\\s*([\\\\\'\\\\"])(?:(?!\\\\2).)*(?-i)Master\\\\.php(?i)\\\\2(?(-2)\\\\))\\\\s*;\\\\s*\\\\?>\\\\s* (?:\\\\s*(?:<!--.*?-->))* <master\\\\s*src=([\\\\\'\\\\\\"])(?<master_url>.+?)\\\\3\\\\/>(?<content>[\\s\\S]*) $ /ix PREG2; $raw = file_get_contents(filter_input(INPUT_SERVER, \'SCRIPT_FILENAME\')); preg_match($re, $raw, $matches); $master = file_get_contents($matches["master_url"]); $child = $matches["content"]; $child_txt = eval2str($child); $master_txt = eval2str($master); $placeholder_xml = new DOMDocument(); @$placeholder_xml->loadHTML($master_txt, LIBXML_NOWARNING); $child_xml = new DOMDocument(); @$child_xml->loadHTML($child_txt, LIBXML_NOWARNING); $child_elems = $child_xml->getElementsByTagName("content"); foreach($child_elems as $c) { $name = $c->getAttribute("name"); $child_map[$name] = $placeholder_xml->importNode($c, true); } $placeholder_elems = $placeholder_xml->getElementsByTagName("placeholder"); while($placeholder_elems->length > 0) { $oldnode = $placeholder_elems->item(0); $name = $oldnode->getAttribute("name"); if(!isset($child_map[$name])) { $newnode = $placeholder_xml->createElement("content"); $attr = $placeholder_xml->createAttribute("name"); $attr->value = $name; $newnode->appendChild($attr); $child_map[$name] = $newnode; } $newnode = $child_map[$name]; $parent = $oldnode->parentNode; $parent->replaceChild($newnode, $oldnode); $placeholder_elems = $placeholder_xml->getElementsByTagName("placeholder"); // } die($placeholder_xml->saveHTML()); // to end execution of the remaining code in the calling file /* */ function eval2str($code) { ob_start(); eval("?>$code"); return ob_get_clean(); } ?>'; preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0); // Print the entire match result var_dump($matches);

Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php