Implementation and detailed explanation of regular expression of email address in PHP

Implementation and detailed explanation of regular expression of email address in PHP_PHP tutorial

WBOY

Release： 2016-07-21 15:19:10

Original

1097 people have browsed it

First attach the code

Copy the code The code is as follows:

^[_.0-9a-z-]+@( [0-9a-z][0-9a-z-]+.)+[a-z]{2,3}$

In this regular expression, "+" means the preceding One or more strings appear continuously; "^" means that the next string must appear at the beginning, "$" means that the previous string must appear at the end;
"." is also ".", here " " is an escape character; "{2,3}" means that the previous string can appear 2-3 times in a row. "()" indicates that the contained content must also appear in the target object. "[_.0-9a-z-]" means any character contained in "_", ".", "-", letters in the range from a to z, and numbers in the range from 0 to 9;
In this way, this regular expression can be translated like this:
"The following characters must be at the beginning (^)", "The characters must be contained in "_", ".", "-", from a to Letters in the z range, numbers in the range 0 to 9 ([_.0-9a-z-])", "The preceding character appears at least once (+)", @, "The string consists of Begins with a letter in the range a to z, a number in the range 0 to 9, followed by at least one character contained in "-", any letter in the range a to z, in the range 0 to 9 Any character in a number ends with . (([0-9a-z][0-9a-z-]+.))", "The previous character appears at least once (+)", "From a to Letters in the z range appear 2-3 times and end with it ([a-z]{2,3}$)"

Copy code The code is as follows:

 
function is_valid_email($email, $test_mx = false) 
{ 
if(eregi("^([_a-z0-9-]+)(.[_a-z0 -9-]+)*@([a-z0-9-]+)(.[a-z0-9-]+)*(.[a-z]{2,4})[ wind_phpcode_0 ]quot;, $ email)) 
if($test_mx) 
{ 
list($username, $domain) = split("@", $email); 
return getmxrr($domain, $mxrecords); 
} 
else 
return true; 
else 
return false; 
} 

The domain name consists of the specific character set, English letters, and numbers of each country's script and "-" (i.e. hyphen or minus sign), but cannot contain "-" at the beginning or end, and "-" cannot appear consecutively in the domain name. The domain name can have up to 60 characters. Bytes (including suffixes .com, .net, .org, etc.)
/^[a-z]([a-z0-9]*[-_]?[a-z0-9]+)*@( [a-z0-9]*[-_]?[a-z0-9]+)+[.][a-z]{2,3}([.][a-z]{2})?$/i;
/content/i constitutes a case-insensitive regular expression;
^ Match start

$ Match end

[a-z] E-Mail prefix must be an English Letters starting with

([a-z0-9]*[-_]?[a-z0-9]+)* match _a_2, aaa11, _1_a_2, but do not match a1_, aaff_33a_, a__aa, If it is a null character, it is also matched, and * means 0 or more.

* represents 0 or more previous characters.

[a-z0-9]* matches 0 or more English letters or numbers

[-_ ]? Matches 0 or 1 "-", because "-" cannot appear continuously

[a-z0-9]+ Matches 1 or more English letters or numbers, because "-" cannot be used as The ending

@ must have @

([a-z0-9]*[-_]?[a-z0-9]+)+ see above ([a-z0 -9]*[-_]?[a-z0-9]+)* explanation, but it cannot be empty, + means one or more.

[.] Treat special characters (.) as ordinary characters

[a-z]{2,3} matches 2 to 3 English letters, usually com or net, etc.

([.][a-z]{2})? Matches 0 or 1 [.][a-z]{2} (such as .cn, etc.) I don’t know if the last part of .com.cn is generally They are all two digits. If not, please modify {2} to {number of starting words, number of ending words}

Perfect E-Mail regular expression, with detailed explanation, please help test it! 2. Extract the email in the string:

Copy the code The code is as follows:

function getEmail ($str) {
$pattern = "/([a-z0-9]*[-_.]?[a-z0-9]+)*@([a-z0-9]*[- _]?[a-z0-9]+)+[.][a-z]{2,3}([.][a-z]{2})?/i";
preg_match_all($pattern,$str . hh@qq.com;.;;,fuyongjie.100@yahoo.com,fu-1999@sina.com";
$emailArr = getEmail($emailstr);
echo "

"; <br>print_r($emailArr); <br>echo "

";
?>Print as follows:
Array
(
[0] =>9999@qq .com.cn
[1] =>fuyongjie@163.com
[2] =>hh@qq.com
[3] =>fuyongjie.100@yahoo.com
[4] =>fu-1999@sina.com
) 3. Comparison: The ^ and $ in the 1st are not included in the regular expression in the 2nd;

Look at the example

Copy code

The code is as follows:

 
function funcemail($str)//Mailbox regular expression
{ 
return (preg_match('/^[_.0-9a-z-a-z-]+@([0-9a- z][0-9a-z-]+.)+[a-z]{2,4}$/',$str))?true:false; 
}//Verification method one
$str= "qbcd@126.com.cn"; 
preg_match("/^[0-9a-z]+@(([0-9a-z]+)[.])+[a-z]{2,3 }$/",$str,$re); 
print_r($re);//Email verification 2
if (eregi("^[_.0-9a-z-]+@([0 -9a-z][0-9a-z-]+.)+[a-z]{2,3}$",$email)) { 
echo "Your email passed the preliminary check"; 
}//The third email verification method

if (ereg("/^[a-z]([a-z0-9]*[-_.]?[a-z0-9]+) *@([a-z0-9]*[-_]?[a-z0-9]+)+[.][a-z]{2,3}([.][a-z]{2})?$ /i; ",$email)){ 
echo "your email address is correct!";} 
　 else{ 
echo "please try again!"; 
} 