What are the requirements for the Mail functions to be available in PHP, particularly in relation to sendmail?

In order for the Mail functions to be available in PHP, particularly in relation to sendmail, the sendmail_path directive in the php.ini file must be correctly configured. This directive specifies the location of the sendmail program on the server. If it is not set or set incorrectly, the Mail functions will not work properly. To fix this issue, you need to ensure that the sendmail_path directive in php.ini points to the correct location of the sendmail program on your server.

// Set the correct path to the sendmail program in php.ini
// Example: 
// For Linux: /usr/sbin/sendmail -t -i
// For Windows: "C:\sendmail\sendmail.exe -t"
ini_set('sendmail_path', '/usr/sbin/sendmail -t -i');