phpif-statementhtml-meta

How do I run a meta tag using php?

I want to run this line of code in a php if statement.How would I do this?

 if (mail("m@me.com",$subject,$ipmessage,$header) ==1){
    echo "Thank You Your Message Has Been Sent!";
    <meta http-equiv="refresh" content="3;url=index.php">
}
Solution 
  •  if (mail("m@me.com",$subject,$ipmessage,$header)){
    echo "Thank You Your Message Has Been Sent!";
  ?>
    <meta http-equiv="refresh" content="3;url=index.php">
 <?php
  }
?>

    For HEADER in php --

    HEADER

    FINAL EDIT -

     if (mail("m@me.com",$subject,$ipmessage,$header)){
    echo "Thank You Your Message Has Been Sent!";
    header("Refresh: 3;index.php");
  }