PHP getmxrr Function

last modified April 4, 2025

The PHP getmxrr function retrieves MX records for a given host. It’s essential for email server validation and configuration checks.

Basic Definition

getmxrr gets the MX (Mail Exchange) records for a hostname. MX records specify mail servers responsible for accepting email messages.

Syntax: getmxrr(string $hostname, array &$hosts, array &$weights = null): bool. Returns true if records exist, false otherwise. Requires DNS server access.

Basic MX Record Check

This example checks if a domain has MX records and displays them.

basic_mx_check.php

<?php

declare(strict_types=1);

$domain = “example.com”; $mxhosts = []; $weights = [];

if (getmxrr($domain, $mxhosts, $weights)) { echo “MX records for $domain:\n”; foreach ($mxhosts as $i => $host) { echo “$host (priority: {$weights[$i]})\n”; } } else { echo “No MX records found for $domain”; }

This checks for MX records and displays each mail server with its priority. Lower priority numbers indicate preferred mail servers.

Email Domain Validation

This demonstrates validating an email domain by checking MX records.

email_validation.php

<?php

declare(strict_types=1);

function isValidEmailDomain($email) { $parts = explode(’@’, $email); if (count($parts) != 2) return false;

$domain = $parts[1];
return getmxrr($domain, $mxhosts);

}

$email = “user@example.com”; echo isValidEmailDomain($email) ? “Valid email domain” : “Invalid email domain”;

This function splits the email to extract the domain, then checks for MX records. This is more reliable than simple format validation.

Getting MX Records with Priorities

This example retrieves and sorts MX records by their priority values.

sorted_mx_records.php

<?php

declare(strict_types=1);

$domain = “example.com”; $mxhosts = []; $weights = [];

if (getmxrr($domain, $mxhosts, $weights)) { $records = array_combine($mxhosts, $weights); asort($records);

echo "Sorted MX records for $domain:\n";
foreach ($records as $host => $priority) {
    echo "Priority $priority: $host\n";
}

} else { echo “No MX records found for $domain”; }

This combines hosts and weights into an array, sorts by priority, and displays the results. Sorting helps identify the preferred mail servers.

Checking Multiple Domains

This shows how to check MX records for multiple domains in one operation.

multiple_domains.php

<?php

declare(strict_types=1);

$domains = [“example.com”, “google.com”, “nonexistent.test”]; $results = [];

foreach ($domains as $domain) { $results[$domain] = getmxrr($domain, $mxhosts) ? “Has MX records” : “No MX records”; }

print_r($results);

This checks multiple domains at once and stores the results in an array. Batch processing is efficient when validating multiple email domains.

Advanced Email Validation

This combines MX record checking with additional email validation steps.

advanced_email_check.php

<?php

declare(strict_types=1);

function validateEmail($email) { // Basic format check if (!filter_var($email, FILTER_VALIDATE_EMAIL)) { return false; }

// Extract domain
$domain = substr(strrchr($email, "@"), 1);

// Check MX records
if (!getmxrr($domain, $mxhosts)) {
    // Fallback to A record check
    return checkdnsrr($domain, "A");
}

return true;

}

$email = “user@example.com”; echo validateEmail($email) ? “Valid email” : “Invalid email”;

This comprehensive validation checks email format, MX records, and falls back to A records if no MX records exist. Provides robust email validation.

Best Practices

• Caching: Cache MX record results to reduce DNS queries

• Error Handling: Handle DNS query failures gracefully

• Timeout: Consider setting timeout for DNS queries

• Validation: Combine with other validation methods

• Fallback: Check A records if no MX records exist

Source

PHP getmxrr Documentation

This tutorial covered the PHP getmxrr function with practical examples for email validation and MX record checking.

Author

My name is Jan Bodnar, and I am a passionate programmer with extensive programming experience. I have been writing programming articles since 2007. To date, I have authored over 1,400 articles and 8 e-books. I possess more than ten years of experience in teaching programming.

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