PHP has its own method to verify whether the email address exists_php tips

There are many ways to verify email addresses in PHP. The most commonly used one is to write regular expressions yourself. However, regular expressions are troublesome. I have PHP’s own method for verification.

filter_var

filter_var is a variable filtering method built into PHP. It provides many practical filters that can be used to verify integers, floating point numbers, email addresses, URLs, MAC addresses, etc.

If filter_var returns false, it means that the variable cannot pass the filter, which means it is illegal.

$email = "lastchiliarch@163.com";
 
var_dump(filter_var($email, FILTER_VALIDATE_EMAIL));
 
 
$email = "asb";
var_dump(filter_var($email, FILTER_VALIDATE_EMAIL));
 
$email = "1@a.com";
var_dump(filter_var($email, FILTER_VALIDATE_EMAIL));

Output:

string(21) "lastchiliarch@163.com"
bool(false)
string(7) <a href="mailto:1@a.com">1@a.com</a>

For the illegal email format asb, it returns false, but for 1@a.com, it passes, but it is still slightly flawed.

However, if the general rules are passed, it will be considered that 1@a.com is a legitimate email address. So is there any way to verify it more accurately?

checkdnsrr

checkdnsrr is actually used to query the DNS record of the specified host. We can use it to verify whether the mailbox exists.

For 1@a.com it must be that the MX record does not exist.

$email = "lastchiliarch@163.com";
  var_dump(checkdnsrr(array_pop(explode("@",$email)),"MX"));
  $email = "1@a.com";
  var_dump(checkdnsrr(array_pop(explode("@",$email)),"MX"));

Output:

  bool(true)
  bool(false)

As you can see, it is perfect. The only drawback is that it is too slow. After all, it is a network request. Therefore, it is not suitable to use this method to verify a large number of mailboxes simultaneously.

filter_var checkdnsrr

We can combine filter_var and checkdnsrr for verification. The vast majority of illegal mailboxes will definitely fail when filter_var is used, and we can use the rest

checkdnsrr for further judgment.

$email_arr = array("lastchiliarch@163.com", "1@a.com");
  foreach($email_arr as $email) {
    if (filter_var($email) === false) {
      echo "invalid email: $email \n";
      continue;
    }
 
    if(checkdnsrr(array_pop(explode("@",$email)),"MX") === false) {
      echo "invalid email: $email \n";
      continue;
    }
  }
 

Output:

invalid email: 1@a.com

But it should be noted that since it is only checking the MX record, it can only determine that 163.com exists, but it cannot prove that the user lastchiliarch exists.

If you want to more accurately determine the existence of the mailbox, you can only connect to the SMTP server to verify it.

Introduced email verification. PHP’s own method how to verify whether the email, URL, and IP are legal. Here is an introduction:

The main thing is to use the filter_var function.

Grammar
filter_var(variable, filter, options)
variable required. Specifies the variables to filter.
filter optional. Specifies the ID of the filter to use.
options specifies an array containing flags/options. Check the possible flags and options for each filter.

PHP Filters

Example #1 A filter_var() example

<&#63;php

var_dump(filter_var('bob@example.com', FILTER_VALIDATE_EMAIL));

var_dump(filter_var('http://example.com', FILTER_VALIDATE_URL, FILTER_FLAG_PATH_REQUIRED));

&#63;>

The above routine will output:

string(15) "bob@example.com"
bool(false)

The above is the entire content of this article. I hope it will be helpful to everyone in php email verification.