{"id":2964,"date":"2025-03-18T23:48:07","date_gmt":"2025-03-18T15:48:07","guid":{"rendered":"https:\/\/www.laixuexila.com\/?p=2964"},"modified":"2025-03-18T23:48:07","modified_gmt":"2025-03-18T15:48:07","slug":"php-%e5%b8%b8%e9%87%8f%ef%bc%88constants%ef%bc%89","status":"publish","type":"post","link":"https:\/\/www.laixuexila.com\/index.php\/2025\/03\/18\/php-%e5%b8%b8%e9%87%8f%ef%bc%88constants%ef%bc%89\/","title":{"rendered":"PHP \u5e38\u91cf\uff08Constants\uff09"},"content":{"rendered":"\n<h2 class=\"wp-block-heading\"><strong>1. \u4ec0\u4e48\u662f\u5e38\u91cf\uff1f<\/strong><\/h2>\n\n\n\n<p>\u5e38\u91cf\uff08Constant\uff09\u662f\u4e00\u4e2a<strong>\u4e0d\u53ef\u6539\u53d8\u7684\u53d8\u91cf<\/strong>\uff0c\u5728 PHP \u8fd0\u884c\u671f\u95f4\u4e00\u65e6\u88ab\u5b9a\u4e49\uff0c\u5c31\u4e0d\u80fd\u518d\u66f4\u6539\u6216\u53d6\u6d88\u5b9a\u4e49\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>2. \u5b9a\u4e49\u5e38\u91cf<\/strong><\/h2>\n\n\n\n<p>PHP \u63d0\u4f9b\u4e24\u79cd\u5b9a\u4e49\u5e38\u91cf\u7684\u65b9\u6cd5\uff1a<\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li><code>define()<\/code>\uff08PHP 5.3+ \u63a8\u8350\uff09<\/li>\n\n\n\n<li><code>const<\/code> \u5173\u952e\u5b57\uff08PHP 5.3+\uff09<\/li>\n<\/ol>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>2.1 \u4f7f\u7528 <code>define()<\/code><\/strong><\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>&lt;?php\ndefine(\"SITE_NAME\", \"MyWebsite\");  \/\/ \u5b9a\u4e49\u4e00\u4e2a\u5e38\u91cf\necho SITE_NAME; \/\/ \u8f93\u51fa: MyWebsite\n?&gt;<\/code><\/pre>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>\u5e38\u91cf\u540d\u79f0<\/strong>\u5fc5\u987b\u662f <strong>\u5b57\u7b26\u4e32<\/strong>\uff0c\u4e14\u901a\u5e38\u91c7\u7528 <strong>\u5168\u5927\u5199<\/strong> \u547d\u540d\u98ce\u683c\u3002<\/li>\n\n\n\n<li><strong>\u4e0d\u80fd\u4f7f\u7528 <code>$<\/code> \u7b26\u53f7<\/strong>\uff08\u5e38\u91cf\u4e0e\u53d8\u91cf\u7684\u533a\u522b\uff09\u3002<\/li>\n\n\n\n<li><code>define()<\/code> <strong>\u53ef\u4ee5\u5728\u6761\u4ef6\u8bed\u53e5\u5185\u5b9a\u4e49<\/strong>\u3002<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>2.2 \u4f7f\u7528 <code>const<\/code><\/strong><\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>&lt;?php\nconst DB_NAME = \"my_database\";\necho DB_NAME; \/\/ \u8f93\u51fa: my_database\n?&gt;<\/code><\/pre>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>const<\/code> \u53ea\u80fd\u7528\u4e8e <strong>\u5168\u5c40\u4f5c\u7528\u57df<\/strong> \u6216 <strong>\u7c7b\u4e2d<\/strong>\uff0c<strong>\u4e0d\u80fd\u5728\u6761\u4ef6\u8bed\u53e5\u6216\u51fd\u6570\u5185\u5b9a\u4e49<\/strong>\u3002<\/li>\n\n\n\n<li><code>const<\/code> <strong>\u5728\u7f16\u8bd1\u65f6\u5b9a\u4e49<\/strong>\uff0c<code>define()<\/code> <strong>\u5728\u8fd0\u884c\u65f6\u5b9a\u4e49<\/strong>\u3002<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>3. \u68c0\u67e5\u5e38\u91cf\u662f\u5426\u5df2\u5b9a\u4e49<\/strong><\/h2>\n\n\n\n<p>\u4f7f\u7528 <code>defined()<\/code> \u51fd\u6570\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>&lt;?php\ndefine(\"VERSION\", \"1.0.0\");\n\nif (defined(\"VERSION\")) {\n    echo \"\u5e38\u91cf VERSION \u5df2\u5b9a\u4e49\";\n} else {\n    echo \"\u5e38\u91cf VERSION \u672a\u5b9a\u4e49\";\n}\n?&gt;<\/code><\/pre>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>4. \u9884\u5b9a\u4e49\u5e38\u91cf<\/strong><\/h2>\n\n\n\n<p>PHP \u63d0\u4f9b\u4e86\u4e00\u4e9b<strong>\u5185\u7f6e\u5e38\u91cf<\/strong>\uff0c\u4f8b\u5982\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>&lt;?php\necho PHP_VERSION;  \/\/ \u8f93\u51fa PHP \u7248\u672c\necho PHP_OS;       \/\/ \u8f93\u51fa PHP \u8fd0\u884c\u7684\u64cd\u4f5c\u7cfb\u7edf\necho __FILE__;     \/\/ \u8f93\u51fa\u5f53\u524d\u6587\u4ef6\u8def\u5f84\necho __LINE__;     \/\/ \u8f93\u51fa\u5f53\u524d\u4ee3\u7801\u884c\u53f7\n?&gt;<\/code><\/pre>\n\n\n\n<p>\u5b8c\u6574\u5217\u8868\u53c2\u8003\u5b98\u65b9\u6587\u6863\uff1a<a href=\"https:\/\/www.php.net\/manual\/zh\/reserved.constants.php\">PHP \u9884\u5b9a\u4e49\u5e38\u91cf<\/a>\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>5. \u5927\u5c0f\u5199\u654f\u611f\u6027<\/strong><\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>define()<\/code> <strong>\u9ed8\u8ba4\u5927\u5c0f\u5199\u654f\u611f<\/strong>\uff1a<\/li>\n<\/ul>\n\n\n\n<pre class=\"wp-block-code\"><code>&lt;?php\ndefine(\"MY_CONSTANT\", \"Hello\");\necho MY_CONSTANT; \/\/ \u8f93\u51fa: Hello\necho my_constant; \/\/ \u9519\u8bef: Undefined constant\n?&gt;<\/code><\/pre>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>const<\/code> <strong>\u603b\u662f\u5927\u5c0f\u5199\u654f\u611f<\/strong>\uff0c\u4e0d\u80fd\u4fee\u6539\u3002<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>6. \u5e38\u91cf\u6570\u7ec4<\/strong><\/h2>\n\n\n\n<p>PHP 5.6+ \u5141\u8bb8\u5b9a\u4e49\u6570\u7ec4\u5e38\u91cf\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>&lt;?php\ndefine(\"COLORS\", &#91;\"Red\", \"Green\", \"Blue\"]);\necho COLORS&#91;0]; \/\/ \u8f93\u51fa: Red\n?&gt;<\/code><\/pre>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>7. \u4f7f\u7528 <code>const<\/code> \u5728\u7c7b\u4e2d\u5b9a\u4e49\u5e38\u91cf<\/strong><\/h2>\n\n\n\n<pre class=\"wp-block-code\"><code>&lt;?php\nclass MyClass {\n    const APP_VERSION = \"2.0.1\";\n}\n\necho MyClass::APP_VERSION; \/\/ \u8f93\u51fa: 2.0.1\n?&gt;<\/code><\/pre>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>\u7c7b\u4e2d\u7684\u5e38\u91cf\u53ea\u80fd\u4f7f\u7528 <code>const<\/code> \u5173\u952e\u5b57<\/strong>\uff0c\u4e0d\u80fd\u4f7f\u7528 <code>define()<\/code>\u3002<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>8. \u9b54\u672f\u5e38\u91cf<\/strong><\/h2>\n\n\n\n<p>PHP \u63d0\u4f9b\u4e86\u4e00\u4e9b <strong>\u9b54\u672f\u5e38\u91cf<\/strong>\uff0c\u5b83\u4eec\u7684\u503c\u4f1a\u968f\u7740\u4e0a\u4e0b\u6587\u53d8\u5316\uff1a<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>\u5e38\u91cf<\/th><th>\u8bf4\u660e<\/th><\/tr><\/thead><tbody><tr><td><code>__LINE__<\/code><\/td><td>\u5f53\u524d\u4ee3\u7801\u884c\u53f7<\/td><\/tr><tr><td><code>__FILE__<\/code><\/td><td>\u5f53\u524d\u6587\u4ef6\u7684\u5b8c\u6574\u8def\u5f84<\/td><\/tr><tr><td><code>__DIR__<\/code><\/td><td>\u5f53\u524d\u6587\u4ef6\u6240\u5728\u76ee\u5f55<\/td><\/tr><tr><td><code>__FUNCTION__<\/code><\/td><td>\u5f53\u524d\u51fd\u6570\u540d\u79f0<\/td><\/tr><tr><td><code>__CLASS__<\/code><\/td><td>\u5f53\u524d\u7c7b\u540d\u79f0<\/td><\/tr><tr><td><code>__METHOD__<\/code><\/td><td>\u5f53\u524d\u65b9\u6cd5\u540d\u79f0<\/td><\/tr><tr><td><code>__NAMESPACE__<\/code><\/td><td>\u5f53\u524d\u547d\u540d\u7a7a\u95f4<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p>\u793a\u4f8b\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>&lt;?php\necho \"\u5f53\u524d\u6587\u4ef6\uff1a\" . __FILE__;\necho \"\u5f53\u524d\u884c\u53f7\uff1a\" . __LINE__;\n?&gt;<\/code><\/pre>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>9. \u7ed3\u8bba<\/strong><\/h2>\n\n\n\n<p>\u2705 <strong>\u5e38\u91cf\u4e0d\u4f1a\u88ab\u4fee\u6539<\/strong>\uff0c\u9002\u7528\u4e8e\u5b58\u50a8\u4e0d\u53ef\u53d8\u7684\u5168\u5c40\u503c\uff08\u5982\u6570\u636e\u5e93\u914d\u7f6e\u3001API \u5bc6\u94a5\uff09\u3002<br>\u2705 <strong><code>define()<\/code> \u66f4\u7075\u6d3b<\/strong>\uff0c\u4f46 <code>const<\/code> <strong>\u66f4\u9002\u5408\u7c7b<\/strong>\u3002<br>\u2705 <strong>\u5c3d\u91cf\u4f7f\u7528 <code>const<\/code> \u5b9a\u4e49\u7c7b\u5e38\u91cf<\/strong>\uff0c\u63d0\u9ad8\u4ee3\u7801\u53ef\u8bfb\u6027\u548c\u5b89\u5168\u6027\u3002<\/p>\n\n\n\n<p>\u66f4\u591a\u8be6\u7ec6\u5185\u5bb9\u8bf7\u5173\u6ce8\u5176\u4ed6\u76f8\u5173\u6587\u7ae0\uff01<\/p>\n","protected":false},"excerpt":{"rendered":"<p>1. \u4ec0\u4e48\u662f\u5e38\u91cf\uff1f \u5e38\u91cf\uff08Constant\uff09\u662f\u4e00\u4e2a\u4e0d\u53ef\u6539\u53d8\u7684\u53d8\u91cf\uff0c\u5728 PHP \u8fd0\u884c\u671f\u95f4\u4e00\u65e6\u88ab\u5b9a\u4e49\uff0c\u5c31\u4e0d\u80fd\u518d\u66f4\u6539 [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":2965,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[80],"tags":[],"class_list":["post-2964","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-php"],"_links":{"self":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/2964","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/comments?post=2964"}],"version-history":[{"count":1,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/2964\/revisions"}],"predecessor-version":[{"id":2966,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/2964\/revisions\/2966"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/media\/2965"}],"wp:attachment":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/media?parent=2964"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/categories?post=2964"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/tags?post=2964"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}