{"id":6961,"date":"2020-01-30T10:37:50","date_gmt":"2020-01-30T10:37:50","guid":{"rendered":"http:\/\/tapchicntt.com\/?p=6961"},"modified":"2020-01-30T11:19:39","modified_gmt":"2020-01-30T11:19:39","slug":"php-bai-3-bien-trong-php","status":"publish","type":"post","link":"https:\/\/tapchicntt.com\/php-bai-3-bien-trong-php\/","title":{"rendered":"[php] B\u00e0i 3: Bi\u1ebfn trong php"},"content":{"rendered":"\n<p>C\u00e1ch ch\u00ednh \u0111\u1ec3 l\u01b0u tr\u1eef th\u00f4ng tin trong ch\u01b0\u01a1ng tr\u00ecnh PHP l\u00e0 s\u1eed d\u1ee5ng m\u1ed9t bi\u1ebfn.<\/p>\n\n\n\n<p>D\u01b0\u1edbi \u0111\u00e2y l\u00e0 nh\u1eefng \u0111i\u1ec1u quan tr\u1ecdng nh\u1ea5t b\u1ea1n n\u00ean bi\u1ebft v\u1ec1 bi\u1ebfn trong PHP.T\u1ea5t c\u1ea3 c\u00e1c bi\u1ebfn trong PHP \u0111\u1ec1u \u0111\u01b0\u1ee3c k\u00ed hi\u1ec7u v\u1edbi d\u1ea5u $ \u1edf \u0111\u1ea7u.<\/p>\n\n\n\n<p>Gi\u00e1 tr\u1ecb c\u1ee7a m\u1ed9t bi\u1ebfn l\u00e0 gi\u00e1 tr\u1ecb c\u1ee7a ph\u00e9p g\u00e1n g\u1ea7n \u0111\u00e2y nh\u1ea5t c\u1ee7a n\u00f3.<\/p>\n\n\n\n<p>C\u00e1c bi\u1ebfn \u0111\u01b0\u1ee3c g\u00e1n v\u1edbi to\u00e1n t\u1eed =, bi\u1ebfn \u1edf b\u00ean tr\u00e1i c\u00f2n bi\u1ec3u th\u1ee9c \u0111\u01b0\u1ee3c \u01b0\u1edbc l\u01b0\u1ee3ng \u1edf b\u00ean ph\u1ea3i.<\/p>\n\n\n\n<p>Bi\u1ebfn c\u00f3 th\u1ec3 ho\u1eb7c  kh\u00f4ng c\u1ea7n \u0111\u01b0\u1ee3c khai b\u00e1o tr\u01b0\u1edbc khi g\u00e1n gi\u00e1 tr\u1ecb. Bi\u1ebfn trong PHP kh\u00f4ng c\u00f3 c\u00e1c ki\u1ec3u n\u1ed9i t\u1ea1i, t\u1ee9c l\u00e0 m\u1ed9t bi\u1ebfn kh\u00f4ng bi\u1ebft tr\u01b0\u1edbc c\u00f3 hay kh\u00f4ng n\u00f3 s\u1ebd \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng \u0111\u1ec3 l\u01b0u tr\u1eef m\u1ed9t s\u1ed1 ho\u1eb7c m\u1ed9t chu\u1ed7i k\u00fd t\u1ef1.<\/p>\n\n\n\n<p>Bi\u1ebfn, \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng tr\u01b0\u1edbc khi ch\u00fang \u0111\u01b0\u1ee3c g\u00e1n, c\u00f3 c\u00e1c gi\u00e1 tr\u1ecb m\u1eb7c \u0111\u1ecbnh.<\/p>\n\n\n\n<p>PHP l\u00e0m r\u1ea5t t\u1ed1t vi\u1ec7c chuy\u1ec3n \u0111\u1ed5i t\u1ef1 \u0111\u1ed9ng t\u1eeb ki\u1ec3u n\u00e0y sang ki\u1ec3u kh\u00e1c khi c\u1ea7n thi\u1ebft.<\/p>\n\n\n\n<p>Bi\u1ebfn trong PHP gi\u1ed1ng v\u1edbi Perl.<\/p>\n\n\n\n<p>PHP c\u00f3 t\u1ed5ng t\u1ea5t c\u1ea3 8 ki\u1ec3u d\u1eef li\u1ec7u m\u00e0 ch\u00fang ta s\u1eed d\u1ee5ng \u0111\u1ec3 x\u00e2y d\u1ef1ng c\u00e1c bi\u1ebfn.<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li><strong>Integer<\/strong>\u00a0\u2212 s\u1ed1 nguy\u00ean. V\u00ed d\u1ee5 1989<\/li><li><strong>Double<\/strong>\u00a0\u2212 s\u1ed1 th\u1ef1c. V\u00ed d\u1ee5 3.14159 hay 49.1.<\/li><li><strong>Boolean<\/strong>\u00a0\u2212 c\u00f3 2 gi\u00e1 tr\u1ecb TRUE ho\u1eb7c FALSE.<\/li><li><strong>NULL<\/strong>\u00a0\u2212 l\u00e0 m\u1ed9t ki\u1ec3u \u0111\u1eb7c bi\u1ec7t, n\u00f3 ch\u1ec9 c\u00f3 gi\u00e1 tr\u1ecb: NULL<\/li><li><strong>String<\/strong>\u00a0\u2212 l\u00e0 chu\u1ed7i c\u00e1c k\u00ed t\u1ef1.<\/li><li><strong>Array<\/strong>\u00a0\u2212 l\u00e0 t\u1eadp h\u1ee3p \u0111\u01b0\u1ee3c \u0111\u1eb7t t\u00ean v\u00e0 l\u1eadp ch\u1ec9 m\u1ee5c c\u1ee7a c\u00e1c gi\u00e1 tr\u1ecb kh\u00e1c.<\/li><li><strong>Object<\/strong>\u00a0\u2212 l\u00e0 instance (s\u1ef1 th\u1ec3 hi\u1ec7n) c\u1ee7a c\u00e1c l\u1edbp m\u00e0 l\u1eadp tr\u00ecnh vi\u00ean t\u1ef1 \u0111\u1ecbnh ngh\u0129a, n\u00f3 c\u00f3 th\u1ec3 \u0111\u00f3ng g\u00f3i c\u00e1c c\u00e1c lo\u1ea1i gi\u00e1 tr\u1ecb v\u00e0 h\u00e0m kh\u00e1c nhau, n\u00f3 d\u00e0nh ri\u00eang cho c\u00e1c l\u1edbp.<\/li><li><strong>Resource<\/strong>\u00a0\u2212 l\u00e0 m\u1ed9t bi\u1ebfn \u0111\u1eb7c bi\u1ec7t n\u00f3 gi\u1eef tham chi\u1ebfu t\u1edbi c\u00e1c t\u00e0i nguy\u00ean ngo\u1ea1i vi \u0111\u1ebfn PHP (v\u00ed d\u1ee5: k\u1ebft n\u1ed1i Database).<\/li><\/ul>\n\n\n\n<p>5 ki\u1ec3u \u0111\u1ea7u ti\u00ean l\u00e0 c\u00e1c\u00a0<strong>ki\u1ec3u bi\u1ebfn \u0111\u01a1n gi\u1ea3n<\/strong>, 2 ki\u1ec3u ti\u1ebfp theo (array v\u00e0 object) l\u00e0 c\u00e1c ki\u1ec3u ph\u1ee9c h\u1ee3p m\u00e0 c\u00f3 th\u1ec3 \u0111\u00f3ng g\u00f3i c\u00e1c gi\u00e1 tr\u1ecb t\u00f9y \u00fd c\u1ee7a c\u00e1c ki\u1ec3u t\u00f9y \u00fd, trong khi c\u00e1c ki\u1ec3u \u0111\u01a1n gi\u1ea3n kh\u00f4ng l\u00e0m \u0111\u01b0\u1ee3c.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Ph\u1ea1m vi bi\u1ebfn trong PHP<\/h2>\n\n\n\n<p>Ph\u1ea1m vi (scope) c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c \u0111\u1ecbnh ngh\u0129a nh\u01b0 l\u00e0 ph\u1ea1m vi kh\u1ea3 d\u1ee5ng c\u1ee7a bi\u1ebfn \u0111\u01b0\u1ee3c khai b\u00e1o trong ch\u01b0\u01a1ng tr\u00ecnh. C\u00e1c bi\u1ebfn trong PHP c\u00f3 th\u1ec3 l\u00e0 m\u1ed9t trong 4 ph\u1ea1m vi sau:<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>Bi\u1ebfn c\u1ee5c b\u1ed9 trong PHP<\/li><li>Tham s\u1ed1 h\u00e0m trong PHP<\/li><li>Bi\u1ebfn to\u00e0n c\u1ee5c trong PHP<\/li><li>Bi\u1ebfn t\u0129nh (hay bi\u1ebfn static) trong PHP<\/li><\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">\u0110\u1eb7t t\u00ean bi\u1ebfn trong PHP<\/h3>\n\n\n\n<p>D\u01b0\u1edbi \u0111\u00e2y l\u00e0 c\u00e1c qui t\u1eafc khi \u0111\u1eb7t t\u00ean m\u1ed9t bi\u1ebfn trong PHP:<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>T\u00ean bi\u1ebfn ph\u1ea3i b\u1eaft \u0111\u1ea7u v\u1edbi m\u1ed9t ch\u1eef c\u00e1i ho\u1eb7c k\u00fd t\u1ef1 d\u1ea5u g\u1ea1ch d\u01b0\u1edbi (_).<\/li><li>M\u1ed9t t\u00ean bi\u1ebfn c\u00f3 th\u1ec3 g\u1ed3m c\u00e1c s\u1ed1, ch\u1eef c\u00e1i, k\u00fd t\u1ef1 d\u1ea5u g\u1ea1ch d\u01b0\u1edbi (_), nh\u01b0ng b\u1ea1n kh\u00f4ng th\u1ec3 s\u1eed d\u1ee5ng c\u00e1c k\u00fd t\u1ef1 nh\u01b0 + , &#8211; , % , ( , ) . &amp; , .v.v.<\/li><\/ul>\n\n\n\n<p>Kh\u00f4ng c\u00f3 gi\u1edbi h\u1ea1n k\u00edch c\u1ee1 cho c\u00e1c bi\u1ebfn trong PHP.<\/p>\n\n\n\n<p><\/p>\n","protected":false},"excerpt":{"rendered":"<p>C\u00e1ch ch\u00ednh \u0111\u1ec3 l\u01b0u tr\u1eef th\u00f4ng tin trong ch\u01b0\u01a1ng tr\u00ecnh PHP l\u00e0 s\u1eed d\u1ee5ng m\u1ed9t bi\u1ebfn. D\u01b0\u1edbi \u0111\u00e2y l\u00e0 nh\u1eefng [&hellip;]<\/p>\n","protected":false},"author":6,"featured_media":4572,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[178],"tags":[],"class_list":["post-6961","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-php"],"views":581,"_links":{"self":[{"href":"https:\/\/tapchicntt.com\/rest-api\/wp\/v2\/posts\/6961","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/tapchicntt.com\/rest-api\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/tapchicntt.com\/rest-api\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/tapchicntt.com\/rest-api\/wp\/v2\/users\/6"}],"replies":[{"embeddable":true,"href":"https:\/\/tapchicntt.com\/rest-api\/wp\/v2\/comments?post=6961"}],"version-history":[{"count":2,"href":"https:\/\/tapchicntt.com\/rest-api\/wp\/v2\/posts\/6961\/revisions"}],"predecessor-version":[{"id":6964,"href":"https:\/\/tapchicntt.com\/rest-api\/wp\/v2\/posts\/6961\/revisions\/6964"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/tapchicntt.com\/rest-api\/wp\/v2\/media\/4572"}],"wp:attachment":[{"href":"https:\/\/tapchicntt.com\/rest-api\/wp\/v2\/media?parent=6961"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/tapchicntt.com\/rest-api\/wp\/v2\/categories?post=6961"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/tapchicntt.com\/rest-api\/wp\/v2\/tags?post=6961"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}