setcookie not working wordpress because of header

问题

I have a WordPress plugin that wants to create cookies but it doesn't work. I would really appreciate a help.

add_shortcode( 'watchlist', 'cwatchlist_short' );
  
function cwatchlist_short() {
	echo '<div class="wrap"><center>';
echo "<form method='POST' action=''";
echo '<p>Please enter the initial of the cryptocurrency or the symbol you want to add to the watchlist!</p> <p>For example: BTC</p>';
	echo "<p><input type='text' name='symbol' placeholder='Initials or symbol'>";
	
	
			echo "<p><input type='submit' value='Submit'>";
			echo "</form></center>";
	echo '</div>';
	if (isset($_POST["symbol"])){
  $x = $_COOKIE['xvalue'] + 1;
setcookie( 'xvalue', $x, time() + 108000, COOKIEPATH, COOKIE_DOMAIN   );

debugging shows: Cannot modify header information - headers already sent by I really need help. Thank you best regards

回答1:

setcookie function can not work on direct page run process, its always throw header already set error message.
To solve this issue must use new function for setcookie & add this function on init action.

For Ex.

add_action( 'init', 'my_setcookie_example' );
function my_setcookie_example() {
	setcookie( "name", "value", time(), "/", COOKIE_DOMAIN );
}

In Your case,need to remove "setcookie( 'xvalue', $x, time() + 108000, COOKIEPATH, COOKIE_DOMAIN );" & place into function, After that add "add_action" hook on place of it.

回答2:

You can't set a cookie in a shortcode function because the headers have already been sent by WordPress. setcookie() defines a cookie to be sent along with the rest of the HTTP headers, so if you want to set a cookie value it needs to be added in a hook prior or during the send_headers hook.

回答3:

Please use ob_start(); function at the top of the file and ob_end_flush() function after the code where you want to use cookies.

ob_start function: Turns on output buffering.

ob_end_clean function: Clears buffer and closes buffering.

For more details http://php.net/manual/en/ref.outcontrol.php

回答4:

Thank you for all of your answers! The OB_START didn't work for me maybe there was a problem in my code but I couldn't use it. The admin post was also a great way to solve it but the easier way for me was to change my code less and I used the add_action inside my function.

add_shortcode( 'watchlist', 'cwatchlist_short' );
  add_action( 'init', 'my_setcookie_example' );
  add_action( 'init', 'my_setcookie_isset');
function my_setcookie_isset() {
if(isset($_COOKIE['xvalue'])){

} else{
setcookie ("xvalue","0",time() + 108000, COOKIEPATH, COOKIE_DOMAIN);
}
if (isset($_COOKIE['thejson'])){
} else{
setcookie ("thejson"," ",time() + 108000, COOKIEPATH, COOKIE_DOMAIN);
}
}
function my_setcookie_example() {
if (isset($_POST["symbol"])){
	   
	    setcookie ("thejson","1",time() + 108000, COOKIEPATH, COOKIE_DOMAIN);

So basically what I did was to add a new function that was going to be run before the header and it checked if the form was completed or not. If textbobx SYMBOL was completed then I set a cookie. Also I set all of my cookies with a nonimportant value to have no error during the process. So if you have a problem except setting a cookie inside a shortcode and a function that check isset of a textbox. Run that function usuing INIT before the header!

Thank you to all because this is my conclusion from all of your answers and ideas and links!

Best Regards

来源：https://stackoverflow.com/questions/50205548/setcookie-not-working-wordpress-because-of-header

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setcookie