How to check the error of mail in php

In PHP, you can check for errors in a mail function using the following methods:

Using the mail() function's return value: The mail() function returns true if the mail is sent successfully, and false if there's an error. You can check the return value to see if there was an error:
```
if (!mail($to, $subject, $message, $headers)) {
 echo "Error sending mail: ". error_get_last()['message'];
}
```
Using the error_get_last() function: The error_get_last() function returns an array containing information about the last error that occurred. You can check the message key in the array to see if there was an error:
```
$error = error_get_last();
if ($error && $error['message']) {
 echo "Error sending mail: ". $error['message'];
}
```
Using the error_log() function: The error_log() function writes an error message to the system's error log. You can check the error log to see if there was an error:
```
error_log("Error sending mail: ". $message);
```

Using a try-catch block: You can wrap your mail function in a try-catch block to catch any exceptions that may occur:

try {
 mail($to, $subject, $message, $headers);
} catch (Exception $e) {
 echo "Error sending mail: ". $e->getMessage();
}

Using a logging library: You can use a logging library like Monolog or Log4PHP to log errors and exceptions.

Some common error messages you might see when sending mail in PHP include:

"Failed to send mail: The following SMTP error was encountered: 530 5.7.0 Must issue a STARTTLS command first"
"Failed to send mail: The following SMTP error was encountered: 553 sorry, that domain isn't in my list of allowed rcpthosts"
"Failed to send mail: The following SMTP error was encountered: 421 4.7.0 Unable to connect to the remote server"

These error messages can help you diagnose and fix issues with your mail function.