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What are atoms in regular expressions in PHP? What content does it consist of? (with code)
What are atoms in regular expressions in PHP? What content does it consist of? (with code)
The previous article introduced you to "What is the delimiter of a regular expression? What do we need to pay attention to? (Attached code) 》, this article continues to introduce to you what are atoms in regular expressions in PHP? What content does it consist of? (With code)
##Atoms in regular expressions
What is an atom:
The smallest unit that makes up a regular expression is an atom.What are the contents of atoms:
- Normal letters are atoms, and all visible characters are atoms.
- Most invisible characters are also atoms, such as: space, \n, \r, \t
- \d represents the number 8- Any character between 9. [e-中
- \D means matching any one character except numbers 0-9
- \s means matching blank characters , including any character among spaces, \n, \r, \t
- \S means matching any one character except whitespace characters
- T \w means matching any character among numbers, uppercase and lowercase letters, and underscores
- W means matching any character except numbers, uppercase and lowercase letters, and underscores.
- []Atom list
- means selecting an atom from the specified characters
- [ 5-9] represents 5, 6, 7, 8, 9 consecutive characters. It is allowed to be abbreviated to the starting character and ending character
- [^ ] Exclusion list
- [^ abc] means that all characters except abc can be used.
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>表单页面</title>
</head>
<body>
<form action= "2.php"method= "post">
<input type="text" name="str" id=""/>
<input type="submit" value="匹配" >
</form>
</body>
</html><?php
//进行匹配
$str = $_POST['str'];
$pattern = '//' ;
//调用正则匹配函数
$result = preg_match($pattern , $str , $match);
echo ' 匹配结果为: '.$result;
echo '<hr/>' ;
if ( $result){
echo '<font color="pink" size="5 ">匹配成功</font>';
}else{
echo '<font color="red">匹配失败</font>';
}
var_dump($match);
?>
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