logout problem

Hello,
suddenly no one can log out my wordpress , w2e are gelling below error

Warning: Cannot modify header information – headers already sent by (output started at /home/megrab/public_html/wp-content/themes/sahifa/custom-functions.php:4) in /home/megrab/public_html/wp-login.php on line 368

Warning: Cannot modify header information – headers already sent by (output started at /home/megrab/public_html/wp-content/themes/sahifa/custom-functions.php:4) in /home/megrab/public_html/wp-login.php on line 380

Warning: Cannot modify header information – headers already sent by (output started at /home/megrab/public_html/wp-content/themes/sahifa/custom-functions.php:4) in /home/megrab/public_html/wp-includes/pluggable.php on line 697

Warning: Cannot modify header information – headers already sent by (output started at /home/megrab/public_html/wp-content/themes/sahifa/custom-functions.php:4) in /home/megrab/public_html/wp-includes/pluggable.php on line 698

Warning: Cannot modify header information – headers already sent by (output started at /home/megrab/public_html/wp-content/themes/sahifa/custom-functions.php:4) in /home/megrab/public_html/wp-includes/pluggable.php on line 699

Warning: Cannot modify header information – headers already sent by (output started at /home/megrab/public_html/wp-content/themes/sahifa/custom-functions.php:4) in /home/megrab/public_html/wp-includes/pluggable.php on line 700

Warning: Cannot modify header information – headers already sent by (output started at /home/megrab/public_html/wp-content/themes/sahifa/custom-functions.php:4) in /home/megrab/public_html/wp-includes/pluggable.php on line 701

Warning: Cannot modify header information – headers already sent by (output started at /home/megrab/public_html/wp-content/themes/sahifa/custom-functions.php:4) in /home/megrab/public_html/wp-includes/pluggable.php on line 702

Warning: Cannot modify header information – headers already sent by (output started at /home/megrab/public_html/wp-content/themes/sahifa/custom-functions.php:4) in /home/megrab/public_html/wp-includes/pluggable.php on line 705

Warning: Cannot modify header information – headers already sent by (output started at /home/megrab/public_html/wp-content/themes/sahifa/custom-functions.php:4) in /home/megrab/public_html/wp-includes/pluggable.php on line 706

Warning: Cannot modify header information – headers already sent by (output started at /home/megrab/public_html/wp-content/themes/sahifa/custom-functions.php:4) in /home/megrab/public_html/wp-includes/pluggable.php on line 707

Warning: Cannot modify header information – headers already sent by (output started at /home/megrab/public_html/wp-content/themes/sahifa/custom-functions.php:4) in /home/megrab/public_html/wp-includes/pluggable.php on line 708

Warning: Cannot modify header information – headers already sent by (output started at /home/megrab/public_html/wp-content/themes/sahifa/custom-functions.php:4) in /home/megrab/public_html/wp-includes/pluggable.php on line 711

Warning: Cannot modify header information – headers already sent by (output started at /home/megrab/public_html/wp-content/themes/sahifa/custom-functions.php:4) in /home/megrab/public_html/wp-includes/pluggable.php on line 712

Warning: Cannot modify header information – headers already sent by (output started at /home/megrab/public_html/wp-content/themes/sahifa/custom-functions.php:4) in /home/megrab/public_html/wp-includes/pluggable.php on line 713

Warning: Cannot modify header information – headers already sent by (output started at /home/megrab/public_html/wp-content/themes/sahifa/custom-functions.php:4) in /home/megrab/public_html/wp-includes/pluggable.php on line 714

Warning: Cannot modify header information – headers already sent by (output started at /home/megrab/public_html/wp-content/themes/sahifa/custom-functions.php:4) in /home/megrab/public_html/wp-includes/pluggable.php on line 876

wish to get help

Thanks