{"id":120750,"date":"2025-11-13T09:00:00","date_gmt":"2025-11-13T02:00:00","guid":{"rendered":"https:\/\/tino.vn\/blog\/?p=120750"},"modified":"2025-11-12T17:44:38","modified_gmt":"2025-11-12T10:44:38","slug":"sua-loi-warning-cannot-modify-header-information-headers-already-sent-by","status":"publish","type":"post","link":"https:\/\/tino.vn\/blog\/sua-loi-warning-cannot-modify-header-information-headers-already-sent-by\/","title":{"rendered":"H\u01b0\u1edbng d\u1eabn s\u1eeda l\u1ed7i Warning: Cannot modify header information &#8211; headers already sent by trong WordPress"},"content":{"rendered":"\n<p><strong>&#8220;Warning: Cannot modify header information &#8211; headers already sent by&#8221; l\u00e0 m\u1ed9t trong nh\u1eefng l\u1ed7i ph\u1ed5 bi\u1ebfn m\u00e0 ng\u01b0\u1eddi d\u00f9ng <a href=\"https:\/\/tino.vn\/blog\/wordpress-la-gi\/\" target=\"_blank\" data-type=\"post\" data-id=\"15589\" rel=\"noreferrer noopener\">WordPress<\/a> th\u01b0\u1eddng g\u1eb7p ph\u1ea3i. L\u1ed7i n\u00e0y c\u00f3 th\u1ec3 khi\u1ebfn trang web c\u1ee7a b\u1ea1n kh\u00f4ng ho\u1ea1t \u0111\u1ed9ng b\u00ecnh th\u01b0\u1eddng, g\u00e2y kh\u00f3 kh\u0103n cho vi\u1ec7c qu\u1ea3n tr\u1ecb ho\u1eb7c l\u00e0m gi\u1ea3m tr\u1ea3i nghi\u1ec7m ng\u01b0\u1eddi d\u00f9ng. C\u00f9ng Tino t\u00ecm hi\u1ec3u nguy\u00ean nh\u00e2n v\u00e0 c\u00e1ch s\u1eeda l\u1ed7i &#8220;Warning: Cannot modify header information &#8211; headers already sent by&#8221; trong WordPress qua b\u00e0i vi\u1ebft n\u00e0y nh\u00e9!<\/strong><\/p>\n\n\n\n<h2 id=\"L\u1ed7i_Warning:_Cannot_modify_header_information_&#8211;_headers_already_sent_by_l\u00e0_g\u00ec?\"><a id=\"post-120750-_bjzpjkevehnn\"><\/a>L\u1ed7i Warning: Cannot modify header information &#8211; headers already sent by l\u00e0 g\u00ec?<\/h2>\n\n\n\n<p>L\u1ed7i &#8220;Warning: Cannot modify header information &#8211; headers already sent by&#8221; l\u00e0 m\u1ed9t th\u00f4ng b\u00e1o l\u1ed7i ph\u1ed5 bi\u1ebfn trong WordPress, x\u1ea3y ra khi c\u00f3 s\u1ef1 c\u1ed1 li\u00ean quan \u0111\u1ebfn vi\u1ec7c g\u1eedi d\u1eef li\u1ec7u \u0111\u1ea7u ra (output) \u0111\u1ebfn tr\u00ecnh duy\u1ec7t tr\u01b0\u1edbc khi c\u00e1c ti\u00eau \u0111\u1ec1 HTTP (headers) \u0111\u01b0\u1ee3c kh\u1edfi t\u1ea1o.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-full\"><img decoding=\"async\" width=\"700\" height=\"400\" src=\"https:\/\/tino.vn\/blog\/wp-content\/uploads\/2025\/11\/sua-loi-Warning-Cannot-modify-header-information-headers-already-sent-by-1.png\" alt=\"L\u1ed7i Warning: Cannot modify header information - headers already sent by l\u00e0 g\u00ec?\" class=\"wp-image-120751\" title=\"\" srcset=\"https:\/\/tino.vn\/blog\/wp-content\/uploads\/2025\/11\/sua-loi-Warning-Cannot-modify-header-information-headers-already-sent-by-1.png 700w, https:\/\/tino.vn\/blog\/wp-content\/uploads\/2025\/11\/sua-loi-Warning-Cannot-modify-header-information-headers-already-sent-by-1-300x171.png 300w\" sizes=\"(max-width: 700px) 100vw, 700px\" \/><figcaption class=\"wp-element-caption\"><strong>L\u1ed7i Warning: Cannot modify header information &#8211; headers already sent by l\u00e0 g\u00ec?<\/strong><\/figcaption><\/figure>\n<\/div>\n\n\n<p>C\u1ee5 th\u1ec3, trong qu\u00e1 tr\u00ecnh ho\u1ea1t \u0111\u1ed9ng c\u1ee7a website, WordPress c\u1ea7n g\u1eedi c\u00e1c ti\u00eau \u0111\u1ec1 HTTP \u0111\u1ec3 qu\u1ea3n l\u00fd phi\u00ean l\u00e0m vi\u1ec7c, chuy\u1ec3n h\u01b0\u1edbng trang ho\u1eb7c x\u00e1c th\u1ef1c ng\u01b0\u1eddi d\u00f9ng. Tuy nhi\u00ean, n\u1ebfu c\u00f3 b\u1ea5t k\u1ef3 n\u1ed9i dung n\u00e0o (k\u1ec3 c\u1ea3 kho\u1ea3ng tr\u1eafng, k\u00fd t\u1ef1 \u1ea9n, ho\u1eb7c m\u00e3 code d\u01b0 th\u1eeba) \u0111\u01b0\u1ee3c g\u1eedi \u0111\u1ebfn tr\u00ecnh duy\u1ec7t tr\u01b0\u1edbc khi c\u00e1c ti\u00eau \u0111\u1ec1 n\u00e0y \u0111\u01b0\u1ee3c x\u1eed l\u00fd, l\u1ed7i s\u1ebd xu\u1ea5t hi\u1ec7n.<\/p>\n\n\n\n<p>\u0110i\u1ec1u n\u00e0y th\u01b0\u1eddng d\u1eabn \u0111\u1ebfn t\u00ecnh tr\u1ea1ng website kh\u00f4ng th\u1ec3 t\u1ea3i \u0111\u00fang c\u00e1ch ho\u1eb7c c\u00e1c ch\u1ee9c n\u0103ng nh\u01b0 \u0111\u0103ng nh\u1eadp, \u0111\u0103ng xu\u1ea5t ho\u1eb7c chuy\u1ec3n h\u01b0\u1edbng b\u1ecb gi\u00e1n \u0111o\u1ea1n, g\u00e2y \u1ea3nh h\u01b0\u1edfng nghi\u00eam tr\u1ecdng \u0111\u1ebfn tr\u1ea3i nghi\u1ec7m ng\u01b0\u1eddi d\u00f9ng v\u00e0 qu\u1ea3n tr\u1ecb website.<\/p>\n\n\n\n<h3 id=\"C\u00e1c_nguy\u00ean_nh\u00e2n_g\u00e2y_ra_l\u1ed7i_Warning:_Cannot_modify_header_information_&#8211;_headers_already_sent_by_trong_WordPress\"><a id=\"post-120750-_z0l0118aaci7\"><\/a><strong>C\u00e1c nguy\u00ean nh\u00e2n g\u00e2y ra l\u1ed7i Warning: Cannot modify header information &#8211; headers already sent by trong WordPress<\/strong><\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Kho\u1ea3ng tr\u1eafng d\u01b0 th\u1eeba trong file PHP: <\/strong>Nguy\u00ean nh\u00e2n ph\u1ed5 bi\u1ebfn nh\u1ea5t l\u00e0 c\u00f3 kho\u1ea3ng tr\u1eafng tr\u01b0\u1edbc th\u1ebb <em>&lt;?php<\/em> ho\u1eb7c sau <em>?&gt;<\/em> trong c\u00e1c file quan tr\u1ecdng nh\u01b0 wp-config.php, functions.php, index.php, &#8230;<\/li>\n\n\n\n<li><strong>Plugin ho\u1eb7c theme kh\u00f4ng t\u01b0\u01a1ng th\u00edch:<\/strong> M\u1ed9t s\u1ed1 plugin ho\u1eb7c theme k\u00e9m ch\u1ea5t l\u01b0\u1ee3ng, ch\u01b0a \u0111\u01b0\u1ee3c c\u1eadp nh\u1eadt ho\u1eb7c kh\u00f4ng t\u01b0\u01a1ng th\u00edch v\u1edbi phi\u00ean b\u1ea3n WordPress hi\u1ec7n t\u1ea1i c\u00f3 th\u1ec3 g\u00e2y ra l\u1ed7i n\u00e0y.<\/li>\n\n\n\n<li><strong>G\u1ecdi h\u00e0m header(), setcookie() ho\u1eb7c session_start() sai c\u00e1ch: <\/strong>Trong PHP, c\u00e1c h\u00e0m nh\u01b0 <em>header()<\/em>, <em>setcookie()<\/em> ho\u1eb7c <em>session_start() <\/em>ph\u1ea3i \u0111\u01b0\u1ee3c g\u1ecdi tr\u01b0\u1edbc khi c\u00f3 b\u1ea5t k\u1ef3 n\u1ed9i dung n\u00e0o \u0111\u01b0\u1ee3c in ra tr\u00ecnh duy\u1ec7t.<\/li>\n\n\n\n<li><strong>File b\u1ecb m\u00e3 h\u00f3a sai \u0111\u1ecbnh d\u1ea1ng (UTF-8 BOM): <\/strong>Khi l\u01b0u file PHP d\u01b0\u1edbi \u0111\u1ecbnh d\u1ea1ng UTF-8 v\u1edbi BOM (Byte Order Mark), m\u1ed9t k\u00fd t\u1ef1 \u1ea9n s\u1ebd \u0111\u01b0\u1ee3c th\u00eam v\u00e0o \u0111\u1ea7u file. \u0110i\u1ec1u n\u00e0y khi\u1ebfn tr\u00ecnh duy\u1ec7t hi\u1ec3u nh\u1ea7m r\u1eb1ng \u0111\u00e3 c\u00f3 d\u1eef li\u1ec7u \u0111\u1ea7u ra, d\u1eabn \u0111\u1ebfn l\u1ed7i.<\/li>\n\n\n\n<li><strong>L\u1ed7i t\u1eeb buffer output (output buffering): <\/strong>N\u1ebfu m\u1ed9t plugin ho\u1eb7c \u0111o\u1ea1n code b\u1eadt <em>output buffering (ob_start())<\/em>, nh\u01b0ng b\u1ecb t\u1eaft kh\u00f4ng \u0111\u00fang c\u00e1ch<em> (ob_end_flush())<\/em>, l\u1ed7i c\u00f3 th\u1ec3 x\u1ea3y ra.<\/li>\n\n\n\n<li><strong>File .htaccess b\u1ecb c\u1ea5u h\u00ecnh sai<\/strong>: N\u1ebfu file n\u00e0y b\u1ecb ch\u1ec9nh s\u1eeda sai c\u00e1ch ho\u1eb7c ch\u1ee9a c\u00e1c quy t\u1eafc kh\u00f4ng h\u1ee3p l\u1ec7, n\u00f3 c\u00f3 th\u1ec3 g\u00e2y ra l\u1ed7i li\u00ean quan \u0111\u1ebfn ti\u00eau \u0111\u1ec1 HTTP.<\/li>\n\n\n\n<li><strong>B\u1ed9 nh\u1edb cache ho\u1eb7c file t\u1ea1m th\u1eddi b\u1ecb l\u1ed7i:<\/strong> D\u1eef li\u1ec7u c\u0169 ho\u1eb7c kh\u00f4ng h\u1ee3p l\u1ec7 c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c g\u1eedi \u0111\u1ebfn tr\u00ecnh duy\u1ec7t tr\u01b0\u1edbc khi ti\u00eau \u0111\u1ec1 HTTP \u0111\u01b0\u1ee3c kh\u1edfi t\u1ea1o.<\/li>\n<\/ul>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-full\"><img decoding=\"async\" width=\"700\" height=\"400\" src=\"https:\/\/tino.vn\/blog\/wp-content\/uploads\/2025\/11\/sua-loi-Warning-Cannot-modify-header-information-headers-already-sent-by-2.png\" alt=\"C\u00e1c nguy\u00ean nh\u00e2n g\u00e2y ra l\u1ed7i Warning: Cannot modify header information - headers already sent by trong WordPress\" class=\"wp-image-120752\" title=\"\" srcset=\"https:\/\/tino.vn\/blog\/wp-content\/uploads\/2025\/11\/sua-loi-Warning-Cannot-modify-header-information-headers-already-sent-by-2.png 700w, https:\/\/tino.vn\/blog\/wp-content\/uploads\/2025\/11\/sua-loi-Warning-Cannot-modify-header-information-headers-already-sent-by-2-300x171.png 300w\" sizes=\"(max-width: 700px) 100vw, 700px\" \/><figcaption class=\"wp-element-caption\"><strong>C\u00e1c nguy\u00ean nh\u00e2n g\u00e2y ra l\u1ed7i Warning: Cannot modify header information &#8211; headers already sent by trong WordPress<\/strong><\/figcaption><\/figure>\n<\/div>\n\n\n<h2 id=\"3_b\u01b0\u1edbc_s\u1eeda_l\u1ed7i_Warning:_Cannot_modify_header_information_&#8211;_headers_already_sent_by_trong_WordPress_\u0111\u01a1n_gi\u1ea3n\"><a id=\"post-120750-_z2sxvq7tfset\"><\/a>3 b\u01b0\u1edbc s\u1eeda l\u1ed7i Warning: Cannot modify header information &#8211; headers already sent by trong WordPress \u0111\u01a1n gi\u1ea3n<\/h2>\n\n\n\n<h3 id=\"1._X\u00e1c_\u0111\u1ecbnh_v\u1ecb_tr\u00ed_l\u1ed7i\"><a id=\"post-120750-_ytx1ytwx8zcs\"><\/a><strong>1. X\u00e1c \u0111\u1ecbnh v\u1ecb tr\u00ed l\u1ed7i<\/strong><\/h3>\n\n\n\n<p>L\u1ed7i \u201cCannot modify header information\u201d th\u01b0\u1eddng \u0111i k\u00e8m v\u1edbi th\u00f4ng tin v\u1ec1 t\u1ec7p v\u00e0 s\u1ed1 d\u00f2ng n\u01a1i l\u1ed7i x\u1ea3y ra. V\u00ed d\u1ee5 nh\u01b0 sau:<\/p>\n\n\n\n<p><em>Warning: Cannot modify header information \u2013 headers already sent by (output started at \/public_html\/wp-content\/plugins\/plugin-name\/function.php:4) in \/public_html\/wp-includes\/pluggable.php on line 1300<\/em><\/p>\n\n\n\n<p>T\u1eeb \u0111\u00f3, ch\u00fang ta bi\u1ebft r\u1eb1ng vi\u1ec7c xu\u1ea5t d\u1eef li\u1ec7u \u0111\u1ea7u ti\u00ean t\u1eeb t\u1ec7p <strong>function.php<\/strong> \u1edf d\u00f2ng <strong>4 <\/strong>\u0111\u00e3 g\u00e2y ra l\u1ed7i khi c\u1ed1 g\u1eafng s\u1eeda \u0111\u1ed5i <strong>header<\/strong> trong t\u1ec7p <strong>pluggable.php<\/strong> t\u1ea1i d\u00f2ng <strong>1300<\/strong>.<\/p>\n\n\n\n<p>\u0110\u1ec3 kh\u1eafc ph\u1ee5c v\u1ea5n \u0111\u1ec1 n\u00e0y, ch\u00fang ta c\u1ea7n ki\u1ec3m tra t\u1ec7p function.php c\u00f3 v\u1ea5n \u0111\u1ec1.<\/p>\n\n\n\n<h3 id=\"2._Ch\u1ec9nh_s\u1eeda_t\u1ec7p_l\u1ed7i\"><a id=\"post-120750-_dhb29597apf2\"><\/a><strong>2. Ch\u1ec9nh s\u1eeda t\u1ec7p l\u1ed7i<\/strong><\/h3>\n\n\n\n<p>Sau khi x\u00e1c \u0111\u1ecbnh \u0111\u01b0\u1ee3c v\u1ecb tr\u00ed l\u1ed7i, b\u1ea1n c\u00f3 th\u1ec3 s\u1eed d\u1ee5ng File Manager c\u1ee7a Hostinger \u0111\u1ec3 ki\u1ec3m tra v\u00e0 lo\u1ea1i b\u1ecf c\u00e1c kho\u1ea3ng tr\u1eafng th\u1eeba trong t\u1ec7p PHP c\u00f3 l\u1ed7i. C\u00e1ch th\u1ef1c hi\u1ec7n nh\u01b0 sau:<\/p>\n\n\n\n<p><strong>B\u01b0\u1edbc 1:<\/strong> Truy c\u1eadp <strong>cPanel<\/strong> \u2192 <strong>File Manager<\/strong>, sau \u0111\u00f3 v\u00e0o c\u00e1c t\u1ec7p c\u1ee7a website WordPress.<\/p>\n\n\n\n<p><strong>B\u01b0\u1edbc 2: <\/strong>T\u00ecm t\u1ec7p g\u1eb7p v\u1ea5n \u0111\u1ec1 d\u1ef1a tr\u00ean th\u00f4ng tin \u1edf ph\u1ea7n <strong>X\u00e1c \u0111\u1ecbnh v\u1ecb tr\u00ed l\u1ed7i<\/strong> (<strong>function.php<\/strong>), sau \u0111\u00f3 nh\u1ea5p \u0111\u00fap v\u00e0o \u0111\u1ec3 m\u1edf.<\/p>\n\n\n\n<p><strong>B\u01b0\u1edbc 3: <\/strong>X\u00f3a kho\u1ea3ng tr\u1eafng tr\u01b0\u1edbc th\u1ebb <strong>&lt;?php <\/strong>ho\u1eb7c sau th\u1ebb \u0111\u00f3ng <strong>?&gt;<\/strong> v\u00e0 d\u00f2ng m\u00e3 cu\u1ed1i c\u00f9ng c\u1ee7a t\u1ec7p. Trong v\u00ed d\u1ee5 d\u01b0\u1edbi \u0111\u00e2y, th\u1ebb <strong>&lt;?php<\/strong> n\u00ean xu\u1ea5t hi\u1ec7n \u1edf d\u00f2ng 1 thay v\u00ec d\u00f2ng 4 v\u00e0 kh\u00f4ng c\u00f3 kho\u1ea3ng tr\u1eafng th\u1eeba.<\/p>\n\n\n\n<p>V\u00ed d\u1ee5:<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-full\"><img decoding=\"async\" width=\"962\" height=\"601\" src=\"https:\/\/tino.vn\/blog\/wp-content\/uploads\/2025\/11\/Screenshot_1-1.png\" alt=\"Ch\u1ec9nh s\u1eeda t\u1ec7p l\u1ed7i\" class=\"wp-image-120754\" title=\"\" srcset=\"https:\/\/tino.vn\/blog\/wp-content\/uploads\/2025\/11\/Screenshot_1-1.png 962w, https:\/\/tino.vn\/blog\/wp-content\/uploads\/2025\/11\/Screenshot_1-1-300x187.png 300w, https:\/\/tino.vn\/blog\/wp-content\/uploads\/2025\/11\/Screenshot_1-1-768x480.png 768w\" sizes=\"(max-width: 962px) 100vw, 962px\" \/><figcaption class=\"wp-element-caption\"><strong>Ch\u1ec9nh s\u1eeda t\u1ec7p l\u1ed7i<\/strong><\/figcaption><\/figure>\n<\/div>\n\n\n<p><strong>B\u01b0\u1edbc 4:<\/strong> L\u01b0u v\u00e0 t\u1ea3i l\u1ea1i trang web \u0111\u1ec3 ki\u1ec3m tra xem l\u1ed7i \u0111\u00e3 \u0111\u01b0\u1ee3c kh\u1eafc ph\u1ee5c ch\u01b0a.<\/p>\n\n\n\n<h3 id=\"3._Thay_th\u1ebf_t\u1ec7p_l\u1ed7i_(n\u1ebfu_c\u1ea7n)\"><a id=\"post-120750-_4p1fjkq2j8ag\"><\/a><strong>3. Thay th\u1ebf t\u1ec7p l\u1ed7i (n\u1ebfu c\u1ea7n)<\/strong><\/h3>\n\n\n\n<p>N\u1ebfu l\u1ed7i xu\u1ea5t ph\u00e1t t\u1eeb m\u1ed9t t\u1ec7p l\u00f5i (core file) c\u1ee7a WordPress, b\u1ea1n c\u00f3 th\u1ec3 thay th\u1ebf t\u1ec7p l\u1ed7i b\u1eb1ng t\u1ec7p m\u1eb7c \u0111\u1ecbnh t\u1eeb g\u00f3i c\u00e0i \u0111\u1eb7t WordPress. C\u00e1ch l\u00e0m nh\u01b0 sau:<\/p>\n\n\n\n<p><strong>B\u01b0\u1edbc 1: <\/strong>T\u1ea3i g\u00f3i <a href=\"https:\/\/wordpress.org\/download\/\" target=\"_blank\" rel=\"noreferrer noopener nofollow\">c\u00e0i \u0111\u1eb7t WordPress<\/a> t\u1eeb website ch\u00ednh th\u1ee9c v\u00e0 gi\u1ea3i n\u00e9n.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-large\"><img decoding=\"async\" width=\"1024\" height=\"568\" src=\"https:\/\/tino.vn\/blog\/wp-content\/uploads\/2025\/11\/sua-loi-Warning-Cannot-modify-header-information-headers-already-sent-by-4-1024x568.png\" alt=\"T\u1ea3i g\u00f3i c\u00e0i \u0111\u1eb7t WordPress\" class=\"wp-image-120755\" title=\"\" srcset=\"https:\/\/tino.vn\/blog\/wp-content\/uploads\/2025\/11\/sua-loi-Warning-Cannot-modify-header-information-headers-already-sent-by-4-1024x568.png 1024w, https:\/\/tino.vn\/blog\/wp-content\/uploads\/2025\/11\/sua-loi-Warning-Cannot-modify-header-information-headers-already-sent-by-4-300x166.png 300w, https:\/\/tino.vn\/blog\/wp-content\/uploads\/2025\/11\/sua-loi-Warning-Cannot-modify-header-information-headers-already-sent-by-4-768x426.png 768w, https:\/\/tino.vn\/blog\/wp-content\/uploads\/2025\/11\/sua-loi-Warning-Cannot-modify-header-information-headers-already-sent-by-4.png 1096w\" sizes=\"(max-width: 1024px) 100vw, 1024px\" \/><figcaption class=\"wp-element-caption\"><strong>T\u1ea3i g\u00f3i c\u00e0i \u0111\u1eb7t WordPress<\/strong><\/figcaption><\/figure>\n<\/div>\n\n\n<p><strong>B\u01b0\u1edbc 2:<\/strong> T\u00ecm t\u1ec7p l\u1ed7i tr\u00ean website WordPress c\u1ee7a b\u1ea1n th\u00f4ng qua <strong>File Manager <\/strong>ho\u1eb7c <strong>FTP client<\/strong>.<\/p>\n\n\n\n<p><strong>B\u01b0\u1edbc 3:<\/strong> X\u00f3a t\u1ec7p b\u1ecb h\u1ecfng v\u00e0 t\u1ea3i l\u00ean t\u1ec7p m\u1edbi t\u1eeb g\u00f3i c\u00e0i \u0111\u1eb7t (tr\u1eeb t\u1ec7p wp-content v\u00e0 file wp-config.php).<\/p>\n\n\n\n<p>T\u1ea3i l\u1ea1i trang web \u0111\u1ec3 ki\u1ec3m tra xem l\u1ed7i \u0111\u00e3 \u0111\u01b0\u1ee3c kh\u1eafc ph\u1ee5c ch\u01b0a.<\/p>\n\n\n\n<p>\u0110\u1ed1i v\u1edbi c\u00e1c l\u1ed7i ph\u00e1t sinh t\u1eeb theme ho\u1eb7c plugin, c\u00e1ch \u0111\u01a1n gi\u1ea3n nh\u1ea5t l\u00e0 c\u00e0i l\u1ea1i theme ho\u1eb7c plugin.<\/p>\n\n\n\n<p>Ngo\u00e0i ra, b\u1ea1n c\u0169ng c\u00f3 th\u1ec3 kh\u00f4i ph\u1ee5c website WordPress t\u1eeb b\u1ea3n sao l\u01b0u n\u1ebfu l\u1ed7i xu\u1ea5t hi\u1ec7n sau khi c\u1eadp nh\u1eadt.<\/p>\n\n\n\n<h3 id=\"K\u1ebft_lu\u1eadn\"><a id=\"post-120750-_g0o78do4vm62\"><\/a><strong>K\u1ebft lu\u1eadn<\/strong><\/h3>\n\n\n\n<p>L\u1ed7i &#8220;Warning: Cannot modify header information &#8211; headers already sent by&#8221; c\u00f3 th\u1ec3 g\u00e2y gi\u00e1n \u0111o\u1ea1n ho\u1ea1t \u0111\u1ed9ng c\u1ee7a website WordPress, nh\u01b0ng ho\u00e0n to\u00e0n c\u00f3 th\u1ec3 kh\u1eafc ph\u1ee5c b\u1eb1ng c\u00e1ch ki\u1ec3m tra v\u00e0 s\u1eeda l\u1ed7i t\u1eebng b\u01b0\u1edbc. Hy v\u1ecdng b\u00e0i vi\u1ebft n\u00e0y s\u1ebd gi\u00fap b\u1ea1n s\u1eeda l\u1ed7i nhanh ch\u00f3ng v\u00e0 \u0111\u1ea3m b\u1ea3o website v\u1eadn h\u00e0nh m\u01b0\u1ee3t m\u00e0! Ch\u00fac b\u1ea1n th\u00e0nh c\u00f4ng!<\/p>\n\n\n\n<h2 id=\"Nh\u1eefng_c\u00e2u_h\u1ecfi_th\u01b0\u1eddng_g\u1eb7p\"><a id=\"post-120750-_qx2qhza08cmp\"><\/a>Nh\u1eefng c\u00e2u h\u1ecfi th\u01b0\u1eddng g\u1eb7p<\/h2>\n\n\n\t\t<section\t\thelp class=\"sc_fs_faq sc_card    \"\n\t\t\t\t>\n\t\t\t\t<h2 id=\"T\u1ea1i_sao_l\u1ed7i_n\u00e0y_v\u1eabn_xu\u1ea5t_hi\u1ec7n_sau_khi_t\u00f4i_\u0111\u00e3_th\u1eed_m\u1ecdi_c\u00e1ch?\">T\u1ea1i sao l\u1ed7i n\u00e0y v\u1eabn xu\u1ea5t hi\u1ec7n sau khi t\u00f4i \u0111\u00e3 th\u1eed m\u1ecdi c\u00e1ch?<\/h2>\t\t\t\t<div>\n\t\t\t\t\t\t<div class=\"sc_fs_faq__content\">\n\t\t\t\t\n\n<p>N\u1ebfu l\u1ed7i v\u1eabn t\u1ed3n t\u1ea1i sau khi b\u1ea1n \u0111\u00e3 th\u1eed t\u1ea5t c\u1ea3 c\u00e1c ph\u01b0\u01a1ng ph\u00e1p, nguy\u00ean nh\u00e2n c\u00f3 th\u1ec3 n\u1eb1m \u1edf:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Hosting ho\u1eb7c c\u1ea5u h\u00ecnh server kh\u00f4ng \u0111\u00fang.<\/li>\n\n\n\n<li>Xung \u0111\u1ed9t s\u00e2u h\u01a1n gi\u1eefa c\u00e1c th\u00e0nh ph\u1ea7n c\u1ee7a website.<\/li>\n<\/ul>\n\n\n\n<p>Trong tr\u01b0\u1eddng h\u1ee3p n\u00e0y, h\u00e3y li\u00ean h\u1ec7 v\u1edbi nh\u00e0 cung c\u1ea5p hosting ho\u1eb7c thu\u00ea chuy\u00ean gia WordPress \u0111\u1ec3 \u0111\u01b0\u1ee3c h\u1ed7 tr\u1ee3.<\/p>\n\n\t\t\t<\/div>\n\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<section\t\thelp class=\"sc_fs_faq sc_card    \"\n\t\t\t\t>\n\t\t\t\t<h2 id=\"T\u00f4i_c\u00f3_n\u00ean_t\u1eaft_ch\u1ebf_\u0111\u1ed9_debug_\u0111\u1ec3_\u1ea9n_l\u1ed7i_n\u00e0y_kh\u00f4ng?\">T\u00f4i c\u00f3 n\u00ean t\u1eaft ch\u1ebf \u0111\u1ed9 debug \u0111\u1ec3 \u1ea9n l\u1ed7i n\u00e0y kh\u00f4ng?<\/h2>\t\t\t\t<div>\n\t\t\t\t\t\t<div class=\"sc_fs_faq__content\">\n\t\t\t\t\n\n<p>T\u1eaft ch\u1ebf \u0111\u1ed9 debug (b\u1eb1ng c\u00e1ch \u0111\u1eb7t WP_DEBUG th\u00e0nh false trong wp-config.php) c\u00f3 th\u1ec3 \u1ea9n th\u00f4ng b\u00e1o l\u1ed7i, nh\u01b0ng kh\u00f4ng th\u1ef1c s\u1ef1 gi\u1ea3i quy\u1ebft v\u1ea5n \u0111\u1ec1. T\u1ed1t nh\u1ea5t l\u00e0 t\u00ecm v\u00e0 s\u1eeda nguy\u00ean nh\u00e2n g\u1ed1c r\u1ec5 thay v\u00ec ch\u1ec9 che gi\u1ea5u tri\u1ec7u ch\u1ee9ng.<\/p>\n\n\t\t\t<\/div>\n\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<section\t\thelp class=\"sc_fs_faq sc_card    \"\n\t\t\t\t>\n\t\t\t\t<h2 id=\"T\u1ea1i_sao_l\u1ed7i_xu\u1ea5t_hi\u1ec7n_sau_khi_c\u1eadp_nh\u1eadt_WordPress,_plugin_ho\u1eb7c_theme?\">T\u1ea1i sao l\u1ed7i xu\u1ea5t hi\u1ec7n sau khi c\u1eadp nh\u1eadt WordPress, plugin ho\u1eb7c theme?<\/h2>\t\t\t\t<div>\n\t\t\t\t\t\t<div class=\"sc_fs_faq__content\">\n\t\t\t\t\n\n<p>C\u1eadp nh\u1eadt c\u00f3 th\u1ec3 l\u00e0m l\u1ed9 ra c\u00e1c v\u1ea5n \u0111\u1ec1 ti\u1ec1m \u1ea9n trong m\u00e3 ngu\u1ed3n, ch\u1eb3ng h\u1ea1n nh\u01b0 plugin kh\u00f4ng t\u01b0\u01a1ng th\u00edch v\u1edbi phi\u00ean b\u1ea3n WordPress m\u1edbi ho\u1eb7c theme ch\u1ee9a l\u1ed7i c\u00fa ph\u00e1p. \u0110\u1ec3 kh\u1eafc ph\u1ee5c, b\u1ea1n c\u00f3 th\u1ec3 kh\u00f4i ph\u1ee5c t\u1eeb b\u1ea3n sao l\u01b0u ho\u1eb7c c\u00e0i \u0111\u1eb7t l\u1ea1i th\u00e0nh ph\u1ea7n g\u00e2y l\u1ed7i.<\/p>\n\n\t\t\t<\/div>\n\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<section\t\thelp class=\"sc_fs_faq sc_card    \"\n\t\t\t\t>\n\t\t\t\t<h2 id=\"L\u1ed7i_n\u00e0y_c\u00f3_\u1ea3nh_h\u01b0\u1edfng_\u0111\u1ebfn_SEO_c\u1ee7a_trang_web_kh\u00f4ng?\">L\u1ed7i n\u00e0y c\u00f3 \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn SEO c\u1ee7a trang web kh\u00f4ng?<\/h2>\t\t\t\t<div>\n\t\t\t\t\t\t<div class=\"sc_fs_faq__content\">\n\t\t\t\t\n\n<p>Tr\u1ef1c ti\u1ebfp th\u00ec kh\u00f4ng, nh\u01b0ng n\u1ebfu l\u1ed7i khi\u1ebfn trang web hi\u1ec3n th\u1ecb tr\u1eafng (white screen) ho\u1eb7c kh\u00f4ng ho\u1ea1t \u0111\u1ed9ng b\u00ecnh th\u01b0\u1eddng s\u1ebd \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn tr\u1ea3i nghi\u1ec7m ng\u01b0\u1eddi d\u00f9ng v\u00e0 th\u1ee9 h\u1ea1ng <a href=\"https:\/\/tino.vn\/blog\/seo-la-gi\/\" target=\"_blank\" data-type=\"post\" data-id=\"16068\" rel=\"noreferrer noopener\">SEO<\/a> gi\u00e1n ti\u1ebfp.<\/p>\n\n\t\t\t<\/div>\n\t\t<\/div>\n\t\t<\/section>\n\t\t\n<script type=\"application\/ld+json\">\n\t{\n\t\t\"@context\": \"https:\/\/schema.org\",\n\t\t\"@type\": \"FAQPage\",\n\t\t\"mainEntity\": [\n\t\t\t\t\t{\n\t\t\t\t\"@type\": \"Question\",\n\t\t\t\t\"name\": \"T\u1ea1i sao l\u1ed7i n\u00e0y v\u1eabn xu\u1ea5t hi\u1ec7n sau khi t\u00f4i \u0111\u00e3 th\u1eed m\u1ecdi c\u00e1ch?\",\n\t\t\t\t\"acceptedAnswer\": {\n\t\t\t\t\t\"@type\": \"Answer\",\n\t\t\t\t\t\"text\": \"<p>N\u1ebfu l\u1ed7i v\u1eabn t\u1ed3n t\u1ea1i sau khi b\u1ea1n \u0111\u00e3 th\u1eed t\u1ea5t c\u1ea3 c\u00e1c ph\u01b0\u01a1ng ph\u00e1p, nguy\u00ean nh\u00e2n c\u00f3 th\u1ec3 n\u1eb1m \u1edf:<\/p><ul><li>Hosting ho\u1eb7c c\u1ea5u h\u00ecnh server kh\u00f4ng \u0111\u00fang.<\/li><li>Xung \u0111\u1ed9t s\u00e2u h\u01a1n gi\u1eefa c\u00e1c th\u00e0nh ph\u1ea7n c\u1ee7a website.<\/li><\/ul><p>Trong tr\u01b0\u1eddng h\u1ee3p n\u00e0y, h\u00e3y li\u00ean h\u1ec7 v\u1edbi nh\u00e0 cung c\u1ea5p hosting ho\u1eb7c thu\u00ea chuy\u00ean gia WordPress \u0111\u1ec3 \u0111\u01b0\u1ee3c h\u1ed7 tr\u1ee3.<\/p>\"\n\t\t\t\t\t\t\t\t\t}\n\t\t\t}\n\t\t\t,\t\t\t\t{\n\t\t\t\t\"@type\": \"Question\",\n\t\t\t\t\"name\": \"T\u00f4i c\u00f3 n\u00ean t\u1eaft ch\u1ebf \u0111\u1ed9 debug \u0111\u1ec3 \u1ea9n l\u1ed7i n\u00e0y kh\u00f4ng?\",\n\t\t\t\t\"acceptedAnswer\": {\n\t\t\t\t\t\"@type\": \"Answer\",\n\t\t\t\t\t\"text\": \"<p>T\u1eaft ch\u1ebf \u0111\u1ed9 debug (b\u1eb1ng c\u00e1ch \u0111\u1eb7t WP_DEBUG th\u00e0nh false trong wp-config.php) c\u00f3 th\u1ec3 \u1ea9n th\u00f4ng b\u00e1o l\u1ed7i, nh\u01b0ng kh\u00f4ng th\u1ef1c s\u1ef1 gi\u1ea3i quy\u1ebft v\u1ea5n \u0111\u1ec1. T\u1ed1t nh\u1ea5t l\u00e0 t\u00ecm v\u00e0 s\u1eeda nguy\u00ean nh\u00e2n g\u1ed1c r\u1ec5 thay v\u00ec ch\u1ec9 che gi\u1ea5u tri\u1ec7u ch\u1ee9ng.<\/p>\"\n\t\t\t\t\t\t\t\t\t}\n\t\t\t}\n\t\t\t,\t\t\t\t{\n\t\t\t\t\"@type\": \"Question\",\n\t\t\t\t\"name\": \"T\u1ea1i sao l\u1ed7i xu\u1ea5t hi\u1ec7n sau khi c\u1eadp nh\u1eadt WordPress, plugin ho\u1eb7c theme?\",\n\t\t\t\t\"acceptedAnswer\": {\n\t\t\t\t\t\"@type\": \"Answer\",\n\t\t\t\t\t\"text\": \"<p>C\u1eadp nh\u1eadt c\u00f3 th\u1ec3 l\u00e0m l\u1ed9 ra c\u00e1c v\u1ea5n \u0111\u1ec1 ti\u1ec1m \u1ea9n trong m\u00e3 ngu\u1ed3n, ch\u1eb3ng h\u1ea1n nh\u01b0 plugin kh\u00f4ng t\u01b0\u01a1ng th\u00edch v\u1edbi phi\u00ean b\u1ea3n WordPress m\u1edbi ho\u1eb7c theme ch\u1ee9a l\u1ed7i c\u00fa ph\u00e1p. \u0110\u1ec3 kh\u1eafc ph\u1ee5c, b\u1ea1n c\u00f3 th\u1ec3 kh\u00f4i ph\u1ee5c t\u1eeb b\u1ea3n sao l\u01b0u ho\u1eb7c c\u00e0i \u0111\u1eb7t l\u1ea1i th\u00e0nh ph\u1ea7n g\u00e2y l\u1ed7i.<\/p>\"\n\t\t\t\t\t\t\t\t\t}\n\t\t\t}\n\t\t\t,\t\t\t\t{\n\t\t\t\t\"@type\": \"Question\",\n\t\t\t\t\"name\": \"L\u1ed7i n\u00e0y c\u00f3 \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn SEO c\u1ee7a trang web kh\u00f4ng?\",\n\t\t\t\t\"acceptedAnswer\": {\n\t\t\t\t\t\"@type\": \"Answer\",\n\t\t\t\t\t\"text\": \"<p>Tr\u1ef1c ti\u1ebfp th\u00ec kh\u00f4ng, nh\u01b0ng n\u1ebfu l\u1ed7i khi\u1ebfn trang web hi\u1ec3n th\u1ecb tr\u1eafng (white screen) ho\u1eb7c kh\u00f4ng ho\u1ea1t \u0111\u1ed9ng b\u00ecnh th\u01b0\u1eddng s\u1ebd \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn tr\u1ea3i nghi\u1ec7m ng\u01b0\u1eddi d\u00f9ng v\u00e0 th\u1ee9 h\u1ea1ng <a>SEO<\/a> gi\u00e1n ti\u1ebfp.<\/p>\"\n\t\t\t\t\t\t\t\t\t}\n\t\t\t}\n\t\t\t\t\t\t]\n\t}\n<\/script>\n","protected":false},"excerpt":{"rendered":"<p>&#8220;Warning: Cannot modify header information &#8211; headers already sent by&#8221; l\u00e0 m\u1ed9t trong nh\u1eefng l\u1ed7i ph\u1ed5 bi\u1ebfn m\u00e0 ng\u01b0\u1eddi d\u00f9ng WordPress th\u01b0\u1eddng g\u1eb7p ph\u1ea3i. L\u1ed7i n\u00e0y c\u00f3 th\u1ec3 khi\u1ebfn trang web c\u1ee7a b\u1ea1n kh\u00f4ng ho\u1ea1t \u0111\u1ed9ng b\u00ecnh th\u01b0\u1eddng, g\u00e2y kh\u00f3 kh\u0103n cho vi\u1ec7c qu\u1ea3n tr\u1ecb ho\u1eb7c l\u00e0m gi\u1ea3m tr\u1ea3i nghi\u1ec7m ng\u01b0\u1eddi d\u00f9ng. C\u00f9ng Tino t\u00ecm [&hellip;]<\/p>\n","protected":false},"author":23,"featured_media":120757,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7382],"tags":[7400],"class_list":["post-120750","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-sua-loi-wordpress","tag-sua-loi-wordpress"],"_links":{"self":[{"href":"https:\/\/tino.vn\/blog\/wp-json\/wp\/v2\/posts\/120750","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/tino.vn\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/tino.vn\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/tino.vn\/blog\/wp-json\/wp\/v2\/users\/23"}],"replies":[{"embeddable":true,"href":"https:\/\/tino.vn\/blog\/wp-json\/wp\/v2\/comments?post=120750"}],"version-history":[{"count":2,"href":"https:\/\/tino.vn\/blog\/wp-json\/wp\/v2\/posts\/120750\/revisions"}],"predecessor-version":[{"id":120758,"href":"https:\/\/tino.vn\/blog\/wp-json\/wp\/v2\/posts\/120750\/revisions\/120758"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/tino.vn\/blog\/wp-json\/wp\/v2\/media\/120757"}],"wp:attachment":[{"href":"https:\/\/tino.vn\/blog\/wp-json\/wp\/v2\/media?parent=120750"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/tino.vn\/blog\/wp-json\/wp\/v2\/categories?post=120750"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/tino.vn\/blog\/wp-json\/wp\/v2\/tags?post=120750"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}