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.
<?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 $domain";
}
This checks for MX records and displays each mail server with its priority. Lower priority numbers indicate preferred mail servers.
Email Domain Validation
This demonstrates validating an email domain by checking MX records.
<?php
declare(strict_types=1);
function isValidEmailDomain($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.
<?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.
<?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.
<?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
This tutorial covered the PHP getmxrr function with practical
examples for email validation and MX record checking.