php - Check if certain HTTP header was defined already -

for wordpress plugin need add p3p http header output.

now need check: if other file defined header, should not overwrite (i.e. not define second time)

like this:

if ( ! header_defined('p3p') ) { // header_defined() need implement     header( 'p3p:cp="..."' ); } 

thanks @rocket hazmat solve problem , came code:

$p3p_done = false; foreach ( headers_list() $header ) {     if ( 0 === stripos( $header, 'p3p:' ) ) {         $p3p_done = true;         break;     } } if ( ! $p3p_done ) { header( 'p3p:cp="noi"' ); }