javascript - Which is the better way , die or echo for ajax response? -

i using ajax in 1 of web pages this. have specified datatype json here.

jquery.ajax({     url:  "www.mydomain.com/ajax.php",     type: "post",     datatype: "json",     data:{to_email_address:"myemail@gmail.com"},     success:function(response){         response = jquery.parsejson(response);         if(response){             alert("success");         }         else{             alert("failed, try again");         }     } }); 

in ajax.php, use echo json_encode function follows

<?php     if(!($mail_to_address, $mail_subject, $content, $headers)) {         echo json_encode(false);     }     else{         echo json_encode(true);     } ?> 

but have seen somewhere , using die instead of echo like

<?php     if(!($mail_to_address, $mail_subject, $content, $headers)) {         die(json_encode(false));     }     else{         die(json_encode(true));     } ?> 

can please explain better way , why? in advance ..

if echo , don't die, run risk of mistakenly producing more output someday required, later down lines.

if die, prints , ends right there. that's difference.

here example using code

<?php     if(!($mail_to_address, $mail_subject, $content, $headers)) {         echo json_encode(false);    // die stop here     }     else{         echo json_encode(true);     }     echo "oops mistakenly printed";  // breaks json ?> 

if use die instead of echo last echo won't break json because never execute.

if know there nothing after conditional checks, or if confident there no special reason use die(), can keep using echo. answer question is: none of them superior other long output under control.