PHP regular expression commonly used functions, php regular expression function_PHP tutorial

PHP regular expression common functions, php regular expression function

1． preg_match()

Function prototype: int preg_match (string $pattern, string $content [, array $matches])
The preg_match () function searches the $content string for content that matches the regular expression given by $pattern. If $matches is provided, the matching results are placed in it. $matches[0] will contain the text that matches the entire pattern, $matches[1] will contain the first captured match of the pattern element enclosed in parentheses, and so on. This function only performs one match and ultimately returns the number of matching results of 0 or 1. Listing 6.1 shows a code example for the preg_match() function.
Code 6.1 Date and time matching
The code is as follows:

<&#63;php 
//需要匹配的字符串。date函数返回当前时间 
$content = "Current date and time is ".date("Y-m-d h:i a").", we are learning PHP together."; 
//使用通常的方法匹配时间 
if (preg_match ("//d{4}-/d{2}-/d{2} /d{2}:/d{2} [ap]m/", $content, $m)) 
{ 
echo "匹配的时间是：" .$m[0]. "/n"; 
} 
//由于时间的模式明显，也可以简单的匹配 
if (preg_match ("/([/d-]{10}) ([/d:]{5} [ap]m)/", $content, $m)) 
{ 
echo "当前日期是：" .$m[1]. "/n"; 
echo "当前时间是：" .$m[2]. "/n"; 
} 
&#63;>

This is a simple dynamic text string matching example. Assuming that the current system time is "13:25 on August 17, 2006", the following content will be output.
The matching time is: 2006-08-17 01:25 pm
The current date is: 2006-08-17
The current time is: 01:25 pm

2． ereg() and eregi()

ereg() is the regular expression matching function in the POSIX extension library. eregi() is a case-ignoring version of the ereg() function. Both have similar functions to preg_match, but the function returns a Boolean value indicating whether the match was successful or not. It should be noted that the first parameter of the POSIX extension library function accepts a regular expression string, that is, no delimiter is required. For example, Listing 6.2 is a method for checking the security of file names.
Code 6.2 Security check of file name
The code is as follows:

<&#63;php 
$username = $_SERVER['REMOTE_USER']; 
$filename = $_GET['file']; 
//对文件名进行过滤，以保证系统安全 
if (!ereg('^[^./][^/]*$', $userfile)) 
{ 
die('这不是一个非法的文件名！'); 
} 
//对用户名进行过滤 
if (!ereg('^[^./][^/]*$', $username)) 
{ 
die('这不是一个无效的用户名'); 
} 
//通过安全过滤，拼合文件路径 
$thefile = "/home/$username/$filename"; 
&#63;>

Typically, using the Perl-compatible regular expression matching function perg_match() will be faster than using ereg() or eregi(). If you just want to find whether a string contains a certain substring, it is recommended to use the strstr() or strpos() function.

Replacement of regular expressions

1． ereg_replace() and eregi_replace()

Function prototype: string ereg_replace (string $pattern, string $replacement, string $string)
string eregi_replace (string $pattern, string $replacement, string $string)
ereg_replace() searches for the pattern string $pattern in $string and replaces the matched result with $replacement. When $pattern contains pattern units (or sub-patterns), positions in $replacement such as "/1" or "$1" will be replaced by the content matched by these sub-patterns. And "/0" or "$0" refers to the content of the entire matching string. It should be noted that the backslash is used as an escape character in double quotes, so the form "//0" and "//1" must be used.
The functions of eregi_replace() and ereg_replace() are the same, except that the former ignores case. Code 6.6 is an application example of this function. This code demonstrates how to do simple cleaning work on the program source code.
Code 6.6 Source code cleaning
The code is as follows:

<&#63;php 
$lines = file('source.php'); //将文件读入数组中 
for($i=0; $i<count($lines); $i++) 
{ 
//将行末以“//”或“#”开头的注释去掉 
$lines[$i] = eregi_replace("(////|#).*$", "", $lines[$i]); 
//将行末的空白消除 
$lines[$i] = eregi_replace("[ /n/r/t/v/f]*$", "/r/n", $lines[$i]); 
} 
//整理后输出到页面 
echo htmlspecialchars(join("",$lines)); 
&#63;>

2． preg_replace()

Function prototype: mixed preg_replace (mixed $pattern, mixed $replacement, mixed $subject [, int $limit])
preg_replace is more powerful than ereg_replace. The first three parameters can all use arrays; the fourth parameter $limit can set the number of replacements, and the default is to replace all. Code 6.7 is an application example of array replacement.
Code 6.7 Array replacement
The code is as follows:

<&#63;php 
//字符串 
$string = "Name: {Name}<br>/nEmail: {Email}<br>/nAddress: {Address}<br>/n"; 
//模式 
$patterns =array( 
"/{Address}/", 
"/{Name}/", 
"/{Email}/" 
); 
//替换字串 
$replacements = array ( 
"No.5, Wilson St., New York, U.S.A", 
"Thomas Ching", 
"tom@emailaddress.com", 
); 
//输出模式替换结果 
print preg_replace($patterns, $replacements, $string); 
&#63;>

The output results are as follows.

Name: Thomas Ching", 
Email: tom@emailaddress.com 
Address: No.5, Wilson St., New York, U.S.A 

The pattern modifier "e" can be used in the regular expression of preg_replace. Its function is to use the matching result as an expression and can be re-operated. For example:
The code is as follows:

<&#63;php 
$html_body = “<HTML><Body><h1 id="TEST">TEST</h1>My Picture<Img src=”my.gif”></Body></HTML>”; 
//输出结果中HTML标签将全部为小写字母 
echo preg_replace ( 
"/(<//&#63;)(/w+)([^>]*>)/e", 
"'//1'.strtolower('//2').'//3'", //此处的模式变量//2将被strtolower转换为小写字符 
$html_body); 
&#63;>

Tips
The preg_replace function uses Perl-compatible regular expression syntax and is generally a faster alternative to ereg_replace. If you only want to do a simple replacement of a string, you can use the str_replace function.

How to use PHP function preg_match_all to test the effect of regular expressions

PHP function preg_match_all code example: php self-study network 2>

How to use PHP function preg_match_all to test the effect of regular expressions

Today we will introduce to you the use of PHP function preg_match_all in regular expression testing. PHP function preg_match_all code example: $html = php self-study networkphp self-study network 2php self-study network 3; PHP dynamic website development skills share the types of PHP printing functions Summarize the details of $_SERVER in PHP Organize the specific usage of the PHP function stristr() Introduce the skills of PHP code performance optimization Explain the PHP function preg_match_all Example requirements: respectively Extract the ID and content of each DIV element, such as biuuu, biuuu_2, biuuu_3, php self-study network, php self-study network 2 and php self-study network 3 (some common website grabbing methods are matched in this way) Analysis: The string is a simple HTML elements, each DIV element corresponds to an ID and content, and is independent. First consider how to extract the ID value and content within a DIV, such as: php self-study network, and then match other similar elements. Two values ​​need to be taken out from a DIV, that is, two matching expressions. The first expression is used to match the ID value (biuuu), and the second expression is used to match the content of the ID (php self-study network). Regular Commonly used expressions use parentheses, then the previous element will become the following form: (php self-study network) (Expression 2) OK, use the parentheses above to divide the areas that need to be matched. The next step is how to match the content in each expression. We guess that an ID may be Letters, numbers or underscores, then this becomes simple, you can use square brackets, as follows: Expression 1: [a-zA-Z0-9_]+ (means to match uppercase and lowercase letters, numbers and underscores) What about Match expression 2, because the content of the ID can be any character, but it should be noted that the characters cannot be matched, because if these two characters are matched, all DIVs used later will be matched, so these need to be excluded. Elements starting with two characters, that is, do not match the characters, as follows: Expression 2: [^]+ (indicates that the characters are not matched) In this way, the PHP function preg_match_all needs The matching subexpression is implemented, but an expression needs to be matched. The method is as follows: Expression: / "(Expression 1)">(Expression 2)/ Note the double quotes "" and / required Use escape characters to escape, and then put the first two expressions in, as follows: "([a-z0-9_]+)">/([^]+)/ This implements a regular expression that matches the ID value and content of each DIV element, and then uses the preg_match_all function to test as follows: $html = php self-study networkphp self-study network 2php self-study network 3>

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