Regular Expressions 101

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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
No Match

r"""
"""
gm

Test String

Substitution

Processing...

Code Generator

Language

Generated Code

$re = '/<img[^>]*alt="([^"]+)"[^>]*>/m'; $str = '<span itemprop="description"> <img src="//res.smzdm.com/images/emotions/30.png" alt="[小怒]" class="wp-smiley"> <img src="//res.smzdm.com/images/emotions/30.png" alt="[小怒]" class="wp-smiley"> <img src="//res.smzdm.com/images/emotions/30.png" alt="[小怒]" class="wp-smiley"> 这文章百度哪里搬来的 </span> <span itemprop="description"> <img src="//res.smzdm.com/images/emotions/36.png" alt="[喜极而泣]" class="wp-smiley"> 年少无知看了那篇文章好奇买了4瓶 喝了一口差点吐出来 </span> <span itemprop="description">国内咋就没厂商做点纯气泡水呢，成本应该不高吧，钱都让屈臣氏巴黎水赚去了 <img src="//res.smzdm.com/images/emotions/23.png" alt="[皱眉]" class="wp-smiley"> </span> <span itemprop="description">小时候就经常煲来喝，利尿排毒 <img src="//res.smzdm.com/images/emotions/45.png" alt="[抽烟]" class="wp-smiley"> </span> <p class="p_content_166651051"><span itemprop="description">我喜欢香草味的，滑滑的感觉 </span></p> <p class="p_content_166650868"><span itemprop="description">我喝过好几箱，后来还回购了，再后来就喝不起了，太贵[皱眉] </span></p>'; $subst = "\g<1>"; $result = preg_replace($re, $subst, $str); echo "The result of the substitution is ".$result;

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