{"id":2553,"date":"2012-05-05T18:19:16","date_gmt":"2012-05-05T18:19:16","guid":{"rendered":"https:\/\/www.jose-aguilar.com\/blog\/?p=2553"},"modified":"2013-01-02T14:34:45","modified_gmt":"2013-01-02T14:34:45","slug":"comprobar-si-una-variable-esta-vacia-en-php","status":"publish","type":"post","link":"https:\/\/www.jose-aguilar.com\/blog\/comprobar-si-una-variable-esta-vacia-en-php\/","title":{"rendered":"Comprobar si una variable est\u00e1 vac\u00eda en PHP"},"content":{"rendered":"<p><a href=\"https:\/\/www.jose-aguilar.com\/blog\/wp-content\/uploads\/2012\/05\/source-php-icon1.png\"><img loading=\"lazy\" decoding=\"async\" class=\"alignleft size-full wp-image-4506\" title=\"source-php-icon\" src=\"https:\/\/www.jose-aguilar.com\/blog\/wp-content\/uploads\/2012\/05\/source-php-icon1.png\" alt=\"\" width=\"128\" height=\"128\" srcset=\"https:\/\/www.jose-aguilar.com\/blog\/wp-content\/uploads\/2012\/05\/source-php-icon1.png 128w, https:\/\/www.jose-aguilar.com\/blog\/wp-content\/uploads\/2012\/05\/source-php-icon1-80x80.png 80w\" sizes=\"auto, (max-width: 128px) 100vw, 128px\" \/><\/a>Al enviar un formulario y recibir con PHP siempre tenemos la necesidad de comprobar si un campo o variable est\u00e1 vac\u00eda o no para proceder a realizar una acci\u00f3n en el caso de que est\u00e9 rellenada o mostrar un mensaje de error en el caso de que est\u00e9 vac\u00eda.<\/p>\n<p>Por ejemplo, si tenemos un bot\u00f3n en nuestro formulario como el siguiente:<\/p>\n<pre>&lt;input type=\"submit\" name=\"enviar\" value=\"Enviar\" \/&gt;<\/pre>\n<p>Tras pulsarlo, en nuestro c\u00f3digo PHP que recibe los datos podemos observar o comprobar si se ha pulsado este bot\u00f3n de la siguiente forma:<\/p>\n<pre>if (isset($_POST['enviar'])) {\r\n   \/\/C\u00f3digo de validaci\u00f3n de datos\r\n}<\/pre>\n<p>La funci\u00f3n isset() determina si una variable est\u00e1 definida y no es NULL.<\/p>\n<p>Si una variable ha sido removida con unset(), esta ya no estar\u00e1 definida. <strong>isset()<\/strong> devolver\u00e1<strong><\/strong> FALSE si prueba una variable que ha sido definida como NULL. Tambi\u00e9n tenga en cuenta que un byte NULL (<em>\u00ab\\0\u00bb<\/em>) no es equivalente a la constante NULL de PHP.<\/p>\n<p>Si son pasados varios par\u00e1metros, entonces <strong>isset()<\/strong> devolver\u00e1 TRUE \u00fanicamente si todos los par\u00e1metros est\u00e1n definidos. La evaluaci\u00f3n se realiza de izquierda a derecha y se detiene tan pronto como se encuentre una variable no definida.<\/p>\n<p>Tambi\u00e9n podr\u00edamos tener un campo en nuestro formulario como el siguiente:<\/p>\n<pre>&lt;input type=\"text\" name=\"username\" \/&gt;<\/pre>\n<p>Y comprobar que contiene valor de la siguiente forma:<\/p>\n<pre>\/\/Si el campo \"username\" est\u00e1 vac\u00edo\r\nif (empty($_POST['username'])) {\r\n  echo \"El campo nombre est\u00e1 vac\u00edo\"; \r\n}<\/pre>\n<p>La funci\u00f3n empty() determina si una variable es considerada vac\u00eda.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Al enviar un formulario y recibir con PHP siempre tenemos la necesidad de comprobar si un campo o variable est\u00e1 vac\u00eda o no para proceder a realizar una acci\u00f3n en el caso de que est\u00e9 rellenada o mostrar un mensaje de error en el caso de que est\u00e9 vac\u00eda. Por ejemplo, si tenemos un bot\u00f3n [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":4506,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3],"tags":[84,79,77],"class_list":["post-2553","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-php","tag-formularios","tag-inputs","tag-validaciones"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v25.6 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Comprobar si una variable est\u00e1 vac\u00eda en PHP - Jose Aguilar Blog<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<meta property=\"og:locale\" content=\"es_ES\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Comprobar si una variable est\u00e1 vac\u00eda en PHP - Jose Aguilar Blog\" \/>\n<meta property=\"og:description\" content=\"Al enviar un formulario y recibir con PHP siempre tenemos la necesidad de comprobar si un campo o variable est\u00e1 vac\u00eda o no para proceder a realizar una acci\u00f3n en el caso de que est\u00e9 rellenada o mostrar un mensaje de error en el caso de que est\u00e9 vac\u00eda. Por ejemplo, si tenemos un bot\u00f3n [&hellip;]\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.jose-aguilar.com\/blog\/comprobar-si-una-variable-esta-vacia-en-php\/\" \/>\n<meta property=\"og:site_name\" content=\"Jose Aguilar Blog\" \/>\n<meta property=\"article:publisher\" content=\"https:\/\/www.facebook.com\/joseaguilarblog\" \/>\n<meta property=\"article:published_time\" content=\"2012-05-05T18:19:16+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2013-01-02T14:34:45+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/www.jose-aguilar.com\/blog\/wp-content\/uploads\/2012\/05\/source-php-icon1.png\" \/>\n\t<meta property=\"og:image:width\" content=\"128\" \/>\n\t<meta property=\"og:image:height\" content=\"128\" \/>\n\t<meta property=\"og:image:type\" content=\"image\/png\" \/>\n<meta name=\"author\" content=\"Jose Aguilar\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:creator\" content=\"@JoseAguilarBlog\" \/>\n<meta name=\"twitter:site\" content=\"@JoseAguilarBlog\" \/>\n<meta name=\"twitter:label1\" content=\"Escrito por\" \/>\n\t<meta name=\"twitter:data1\" content=\"Jose Aguilar\" \/>\n\t<meta name=\"twitter:label2\" content=\"Tiempo de lectura\" \/>\n\t<meta name=\"twitter:data2\" content=\"1 minuto\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"WebPage\",\"@id\":\"https:\/\/www.jose-aguilar.com\/blog\/comprobar-si-una-variable-esta-vacia-en-php\/\",\"url\":\"https:\/\/www.jose-aguilar.com\/blog\/comprobar-si-una-variable-esta-vacia-en-php\/\",\"name\":\"Comprobar si una variable est\u00e1 vac\u00eda en PHP - Jose Aguilar Blog\",\"isPartOf\":{\"@id\":\"https:\/\/www.jose-aguilar.com\/blog\/#website\"},\"primaryImageOfPage\":{\"@id\":\"https:\/\/www.jose-aguilar.com\/blog\/comprobar-si-una-variable-esta-vacia-en-php\/#primaryimage\"},\"image\":{\"@id\":\"https:\/\/www.jose-aguilar.com\/blog\/comprobar-si-una-variable-esta-vacia-en-php\/#primaryimage\"},\"thumbnailUrl\":\"https:\/\/www.jose-aguilar.com\/blog\/wp-content\/uploads\/2012\/05\/source-php-icon1.png\",\"datePublished\":\"2012-05-05T18:19:16+00:00\",\"dateModified\":\"2013-01-02T14:34:45+00:00\",\"author\":{\"@id\":\"https:\/\/www.jose-aguilar.com\/blog\/#\/schema\/person\/e6d485db1e1140866e95971d17105d11\"},\"breadcrumb\":{\"@id\":\"https:\/\/www.jose-aguilar.com\/blog\/comprobar-si-una-variable-esta-vacia-en-php\/#breadcrumb\"},\"inLanguage\":\"es\",\"potentialAction\":[{\"@type\":\"ReadAction\",\"target\":[\"https:\/\/www.jose-aguilar.com\/blog\/comprobar-si-una-variable-esta-vacia-en-php\/\"]}]},{\"@type\":\"ImageObject\",\"inLanguage\":\"es\",\"@id\":\"https:\/\/www.jose-aguilar.com\/blog\/comprobar-si-una-variable-esta-vacia-en-php\/#primaryimage\",\"url\":\"https:\/\/www.jose-aguilar.com\/blog\/wp-content\/uploads\/2012\/05\/source-php-icon1.png\",\"contentUrl\":\"https:\/\/www.jose-aguilar.com\/blog\/wp-content\/uploads\/2012\/05\/source-php-icon1.png\",\"width\":128,\"height\":128},{\"@type\":\"BreadcrumbList\",\"@id\":\"https:\/\/www.jose-aguilar.com\/blog\/comprobar-si-una-variable-esta-vacia-en-php\/#breadcrumb\",\"itemListElement\":[{\"@type\":\"ListItem\",\"position\":1,\"name\":\"Portada\",\"item\":\"https:\/\/www.jose-aguilar.com\/blog\/\"},{\"@type\":\"ListItem\",\"position\":2,\"name\":\"Comprobar si una variable est\u00e1 vac\u00eda en PHP\"}]},{\"@type\":\"WebSite\",\"@id\":\"https:\/\/www.jose-aguilar.com\/blog\/#website\",\"url\":\"https:\/\/www.jose-aguilar.com\/blog\/\",\"name\":\"Jose Aguilar Blog\",\"description\":\"Desarrollo Web con PrestaShop, WordPress, PHP, jQuery y Ajax\",\"potentialAction\":[{\"@type\":\"SearchAction\",\"target\":{\"@type\":\"EntryPoint\",\"urlTemplate\":\"https:\/\/www.jose-aguilar.com\/blog\/?s={search_term_string}\"},\"query-input\":{\"@type\":\"PropertyValueSpecification\",\"valueRequired\":true,\"valueName\":\"search_term_string\"}}],\"inLanguage\":\"es\"},{\"@type\":\"Person\",\"@id\":\"https:\/\/www.jose-aguilar.com\/blog\/#\/schema\/person\/e6d485db1e1140866e95971d17105d11\",\"name\":\"Jose Aguilar\",\"image\":{\"@type\":\"ImageObject\",\"inLanguage\":\"es\",\"@id\":\"https:\/\/www.jose-aguilar.com\/blog\/#\/schema\/person\/image\/\",\"url\":\"https:\/\/secure.gravatar.com\/avatar\/abbfef5f1d75260c549d0f2c2842bb697ba1aadff3b2836b39d2590c8a625415?s=96&d=mm&r=g\",\"contentUrl\":\"https:\/\/secure.gravatar.com\/avatar\/abbfef5f1d75260c549d0f2c2842bb697ba1aadff3b2836b39d2590c8a625415?s=96&d=mm&r=g\",\"caption\":\"Jose Aguilar\"},\"description\":\"Director ejecutivo y tecnol\u00f3gico en JA Modules. 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