PHP Conditional Statements. Very often when you write code, you want to perform different actions for different conditions. You can use conditional statements in your code to do this. In PHP we have the following conditional statements: if statement - executes some code if one condition is true Facebook. Email or phone: Password: Forgot account? Create new account. Aug 1, 2023 · This function doesn't always produce the expected results if you have a needle that isn't UTF-8 but are looking for it in a UTF-8 string. This won't be a concern for most people, but if you are mixing old and new data, especially if reading data from a file, it could be an issue. Aug 1, 2023 · PHP supports C-style pre- and post-increment and decrement operators. Note: The increment/decrement operators only affect numbers and strings. Arrays, objects, booleans and resources are not affected. Decrementing null values has no effect too, but incrementing them results in 1. Increment/decrement Operators. 2 years ago. In php there are 3 types of comments. 1.single line c++ style comment (//) 2.single line Unix shell stype comment (#) 3.multi line c style comment (/*/) single or multi line comment comes to the end of the line or come first to the current block of php code.PHP: PHP 8.0.0 Release Announcement. PHP 8.1.23 Released! Change language: Released! PHP 8.0 is a major update of the PHP language. It contains many new features and optimizations including named arguments, union types, attributes, constructor property promotion, match expression, nullsafe operator, JIT, and improvements in the type system ...PHP: Hypertext Preprocessor. popular general-purpose scripting language that is especially suited to web development. Fast, flexible and pragmatic, PHP powers everything from your blog to the most popular websites in the world. What's new in 8.2 Download. 8.2.9 · Changelog · Upgrading.Example Get your own PHP Server. When the user fills out the form above and clicks the submit button, the form data is sent for processing to a PHP file named "welcome.php". The form data is sent with the HTTP POST method. To display the submitted data you could simply echo all the variables. The "welcome.php" looks like this: Just like any other programming language, PHP also supports various types of operations like arithmetic operations (addition, subtraction, etc), logical operations (AND, OR etc), Increment/Decrement Operations, etc. Thus, PHP provides us with many operators to perform such operations on various operands or variables, or values.Where src/ is the directory containing all your PHP code. Then, run the commands to build and run the Docker image: $ docker build -t my-php-app . $ docker run -d --name my-running-app my-php-app. We recommend that you add a php.ini configuration file; see the "Configuration" section for details. The PHP concatenation operator (.) is used to combine two string values to create one string. .=. Concatenation assignment.by Tali Smith. The fastest and easiest way to install PHP on Internet Information Services (IIS) is by using the Microsoft® Web Platform Installer (Web PI). Web PI completely automates setting up IIS, FastCGI, and the latest version of PHP from the php.net Web site. With Web PI, you can navigate to the "Web Platform" tab and select "PHP" under ...Facebook. Email or phone: Password: Forgot account? Create new account.Aug 1, 2023 · The simplest way to specify a string is to enclose it in single quotes (the character ' ). To specify a literal single quote, escape it with a backslash ( \ ). To specify a literal backslash, double it ( \\ ). All other instances of backslash will be treated as a literal backslash: this means that the other escape sequences you might be used to ... PHP - Keep The Values in The Form. To show the values in the input fields after the user hits the submit button, we add a little PHP script inside the value attribute of the following input fields: name, email, and website. In the comment textarea field, we put the script between the <textarea> and </textarea> tags. A session is started with the session_start () function. Session variables are set with the PHP global variable: $_SESSION. Now, let's create a new page called "demo_session1.php". In this page, we start a new PHP session and set some session variables: The optional timestamp parameter in the date () function specifies a timestamp. If omitted, the current date and time will be used (as in the examples above). The PHP mktime () function returns the Unix timestamp for a date. The Unix timestamp contains the number of seconds between the Unix Epoch (January 1 1970 00:00:00 GMT) and the time ... Arrays. ¶. An array in PHP is actually an ordered map. A map is a type that associates values to keys. This type is optimized for several different uses; it can be treated as an array, list (vector), hash table (an implementation of a map), dictionary, collection, stack, queue, and probably more. As array values can be other array s, trees and ...8.1. Release Date 2021-11-25. Version Status Supported. PHP 8.1, released in 2021, brings major new features such as Enums, Fibers, never return type, Intersection Types, readonly properties, and more, while ironing out some of its undesired legacy features by deprecating them.在 PHP 中，赋值运算符 = 用于给变量赋值。 在 PHP 中，算术运算符 + 用于把值加在一起。 PHP 算术运算符 运算符 名称 描述 实例 结果 x + y 加 x 和 y 的和 2 + 2 4 x - y 减 x 和 y 的差 5 - 2 3 x * y 乘 x 和 y 的积 5 * 2 10 x / y 除 x 和 y 的商 15 /.. PHP Operators. PHP Operator is a symbol i.e used to perform operations on operands. In simple words, operators are used to perform operations on variables or values.Click on the URL button, Enter URL and Submit. This tool supports loading the PHP File to beautify. Click on the Upload button and select File. It beautify pure PHP framework file such as Laravel, CodeIgniter, YII, CakePHP, Symfony and many more one file at a time. PHP Source Code Beautifier Online works well on Windows, MAC, Linux, Chrome ...Dec 19, 2021 · Just like any other programming language, PHP also supports various types of operations like arithmetic operations (addition, subtraction, etc), logical operations (AND, OR etc), Increment/Decrement Operations, etc. Thus, PHP provides us with many operators to perform such operations on various operands or variables, or values. pub 2048R/31CBD89E 2016-12-08 Key fingerprint = 5289 95BF EDFB A719 1D46 839E F9BA 0ADA 31CB D89E uid Joe Watkins <[email protected]> pub rsa4096 2021-04-26 [SC] [expires: 2025-11-24] 39B6 4134 3D8C 104B 2B14 6DC3 F9C3 9DC0 B969 8544 uid [ultimate] Ben Ramsey <[email protected]> sub rsa4096 2021-04-26 [E] [expires: 2025-11-24] pub rsa4096 2021-04-01 [SC] F1F6 9223 8FBC 1666 E5A5 CCD4 199F 9DFE F6FF ...8.1. Release Date 2021-11-25. Version Status Supported. PHP 8.1, released in 2021, brings major new features such as Enums, Fibers, never return type, Intersection Types, readonly properties, and more, while ironing out some of its undesired legacy features by deprecating them.Aug 1, 2023 · 2 years ago. In php there are 3 types of comments. 1.single line c++ style comment (//) 2.single line Unix shell stype comment (#) 3.multi line c style comment (/*/) single or multi line comment comes to the end of the line or come first to the current block of php code. [SERVER_SOFTWARE] => PHP 7.1.0 Development Server [SERVER_PROTOCOL] => HTTP/1.1 [SERVER_NAME] => 0.0.0.0 [SERVER_PORT] => 8080 [REQUEST_URI] => / [REQUEST_METHOD] => GET [SCRIPT_NAME] => /index.php [SCRIPT_FILENAME] => E:\Programs\PHPServer\www\srv\index.php [PHP_SELF] => /index.php [HTTP_HOST] => www.wuxiancheng.cn:8080 [HTTP_CONNECTION ...PHP is an open-source, interpreted, and object-oriented scripting language that can be executed at the server-side. PHP is well suited for web development. Therefore, it is used to develop web applications (an application that executes on the server and generates the dynamic page.). PHP was created by Rasmus Lerdorf in 1994 but appeared in the ...Partitioning up long code blocks really helps to locate the origin of syntax errors. Comment out offending code. If you can't isolate the problem source, start to comment out (and thus temporarily remove) blocks of code. As soon as you got rid of the parsing error, you have found the problem source.Aug 1, 2023 · Here's how to run dual PHP instances with PHP 5.2 and any previous PHP on Windows 2003: 1. Right-click My Computer, go to Advanced tab, and click on Environment Variables. Add the two installations and their EXT directories to the Path variable. For example, add: c:\php;c:\php\ext;c:\TMAS\php;c:\tmas\php\ext; Aug 1, 2023 · Here we would like to show the very basics of PHP in a short, simple tutorial. This text only deals with dynamic web page creation with PHP, though PHP is not only capable of creating web pages. See the section titled What can PHP do for more information. PHP-enabled web pages are treated just like regular HTML pages and you can create and edit ... Aug 1, 2023 · PHP (recursive acronym for PHP: Hypertext Preprocessor) is a widely-used open source general-purpose scripting language that is especially suited for web development and can be embedded into HTML. PHP is a recursive acronym for "PHP: Hypertext Preprocessor". PHP is a server side scripting language that is embedded in HTML. It is used to manage dynamic content, databases, session tracking, even build entire e-commerce sites. It is integrated with a number of popular databases, including MySQL, PostgreSQL, Oracle, Sybase, Informix, and ...Aug 1, 2023 · PHP (recursive acronym for PHP: Hypertext Preprocessor) is a widely-used open source general-purpose scripting language that is especially suited for web development and can be embedded into HTML. Aug 18, 2023 · Step 1- Create a HTML PHP Login Form. Step 2: Create a CSS Code for Website Design. View More. In today's digital age, the importance of online security cannot be ignored. As a result, creating a login form is an essential feature for any website that requires user authentication. The following is a guide on creating a login form in PHP. PHP Programming at Wikibooks. PHP is a general-purpose scripting language geared towards web development. [9] It was originally created by Danish-Canadian programmer Rasmus Lerdorf in 1993 and released in 1995. [10] [11] The PHP reference implementation is now produced by the PHP Group. [12] PHP was originally an abbreviation of Personal Home ...PHP is a server-side scripting language created in 1995 by Rasmus Lerdorf. PHP is a widely-used open source general-purpose scripting language that is especially suited for web development and can be embedded into HTML. What is PHP used for? As of October 2018, PHP is used on 80% of websites whose server-side language is known. It is typically ...8.1. Release Date 2021-11-25. Version Status Supported. PHP 8.1, released in 2021, brings major new features such as Enums, Fibers, never return type, Intersection Types, readonly properties, and more, while ironing out some of its undesired legacy features by deprecating them.Where src/ is the directory containing all your PHP code. Then, run the commands to build and run the Docker image: $ docker build -t my-php-app . $ docker run -d --name my-running-app my-php-app. We recommend that you add a php.ini configuration file; see the "Configuration" section for details.Getting Started Introduction A simple tutorial Language Reference Basic syntax Types Variables Constants Expressions Operators Control Structures FunctionsPhp login script is used to provide the authentication for our web pages. the Script executes after submitting the user login button. Login Page Login page should be as follows and works based on session. According to the PHP Manual, the '=>' created key/value pairs. Also, Equal or Greater than is the opposite way: '>='. In PHP the greater or less than sign always goes first: '>=', '<='. And just as a side note, excluding the second value does not work like you think it would. Instead of only giving you the key, It actually only gives you a value:pub 2048R/31CBD89E 2016-12-08 Key fingerprint = 5289 95BF EDFB A719 1D46 839E F9BA 0ADA 31CB D89E uid Joe Watkins <[email protected]> pub rsa4096 2021-04-26 [SC] [expires: 2025-11-24] 39B6 4134 3D8C 104B 2B14 6DC3 F9C3 9DC0 B969 8544 uid [ultimate] Ben Ramsey <[email protected]> sub rsa4096 2021-04-26 [E] [expires: 2025-11-24] pub rsa4096 2021-04-01 [SC] F1F6 9223 8FBC 1666 E5A5 CCD4 199F 9DFE F6FF ... PHP is an open-source, interpreted, and object-oriented scripting language that can be executed at the server-side. PHP is well suited for web development. Therefore, it is used to develop web applications (an application that executes on the server and generates the dynamic page.). PHP was created by Rasmus Lerdorf in 1994 but appeared in the ...Jan 30, 2023 · 8.1. Release Date 2021-11-25. Version Status Supported. PHP 8.1, released in 2021, brings major new features such as Enums, Fibers, never return type, Intersection Types, readonly properties, and more, while ironing out some of its undesired legacy features by deprecating them. PHP is an open-source, interpreted, and object-oriented scripting language that can be executed at the server-side. PHP is well suited for web development. Therefore, it is used to develop web applications (an application that executes on the server and generates the dynamic page.). PHP was created by Rasmus Lerdorf in 1994 but appeared in the ...Dec 26, 2012 · The double arrow operator, =>, is used as an access mechanism for arrays. This means that what is on the left side of it will have a corresponding value of what is on the right side of it in array context. This can be used to set values of any acceptable type into a corresponding index of an array. The index can be associative (string based) or ... Mar 20, 2013 · 1. For me, the PHP path traversed from php5.6.25 (or php7) installation folder, through wamp folder, bin and php... C:\wamp64\bin\php\php5.6.25>. In similar way other providers like WAMP/XAMPP on windows have PHP installed under <provider-base-dir>\bin\php directory (even multiple PHP version come from there. The POST Method. The POST method transfers information via HTTP headers. The information is encoded as described in case of GET method and put into a header called QUERY_STRING. The POST method does not have any restriction on data size to be sent. The POST method can be used to send ASCII as well as binary data.The Definitive PHP 7.2, 7.3, 7.4, 8.0, and 8.1 Benchmarks (2023) The year 2021 has been highly eventful for PHP ( and Kinsta ). PHP 8.0 is already a year old, and the much-anticipated PHP 8.1 was released on November 25, 2021, bringing many exciting features. You can catch up on all the latest PHP 8.1 features in our in-depth post.The PHP concatenation operator (.) is used to combine two string values to create one string. .=. Concatenation assignment.Aug 1, 2023 · However, PHP Manual is not listed "(" and ")" in precedence list. It looks like "(" and ")" has higher precedence as it should be. Note: If you write following code, you would need "()" to get expected value. Where src/ is the directory containing all your PHP code. Then, run the commands to build and run the Docker image: $ docker build -t my-php-app . $ docker run -d --name my-running-app my-php-app. We recommend that you add a php.ini configuration file; see the "Configuration" section for details. PHP-GTK related documentation is hosted on the PHP-GTK website. Documentation of PEAR and the various packages can be found on a separate server. You can still read a copy of the original PHP/FI 2.0 Manual on our site, which we only host for historical purposes. The same applies to the PHP 3 Manual .The double arrow operator, =>, is used as an access mechanism for arrays. This means that what is on the left side of it will have a corresponding value of what is on the right side of it in array context. This can be used to set values of any acceptable type into a corresponding index of an array. The index can be associative (string based) or ...This package was approved as a trusted package on 30 Aug 2023. Description. PHP is an HTML-embedded scripting language. Much of its syntax is borrowed from C, Java and Perl with a couple of unique PHP-specific features thrown in. The goal of the language is to allow web developers to write dynamically generated pages quickly.Formatter. This PHP formatter allows you to make your code readable so you can edit it in a more simple fashion. Autodetect HTML XML CSS JavaScript PHP JSON. xxxxxxxxxx. 1. Tab size.Display PHP errors via .htaccess configuration. Developers usually have access to the directory files. The directive for showing PHP errors can also be enabled or disabled using the .htaccess file located in the root or public directory of the project. php_flag display_startup_errors on php_flag display_errors onThe simplest method to determine the PHP version running on your website is executing a PHP file that contains the following code: <?php echo 'PHP version: ' . phpversion(); Create the file using a text editor like gedit or Notepad, and upload it to your website’s document root directory.The user friendly PHP online compiler that allows you to Write PHP code and run it online. The PHP text editor also supports taking input from the user and standard libraries. It uses the PHP compiler to compile code.Jan 30, 2023 · 8.1. Release Date 2021-11-25. Version Status Supported. PHP 8.1, released in 2021, brings major new features such as Enums, Fibers, never return type, Intersection Types, readonly properties, and more, while ironing out some of its undesired legacy features by deprecating them. Getting Started Introduction A simple tutorial Language Reference Basic syntax Types Variables Constants Expressions Operators Control Structures Functionsلغة PHP (والتي هي اختصارٌ تعاودي للعبارة PHP: Hypertext Preprocessor) هي لغةٌ مفتوحة المصدر شائعة الاستخدام لها مجال استخدامٍ عامٍ لكنها تناسب تطوير الويب ودمج لغة HTML معها. الذي يُميّز PHP عن الشيفرات التي ... PHP Programming at Wikibooks. PHP is a general-purpose scripting language geared towards web development. [9] It was originally created by Danish-Canadian programmer Rasmus Lerdorf in 1993 and released in 1995. [10] [11] The PHP reference implementation is now produced by the PHP Group. [12] PHP was originally an abbreviation of Personal Home ...PHP Variables. A variable can have a short name (like x and y) or a more descriptive name (age, carname, total_volume). A variable starts with the $ sign, followed by the name of the variable. A variable name must start with a letter or the underscore character. A variable name can only contain alpha-numeric characters and underscores (A-z, 0-9 ...Dec 19, 2021 · Just like any other programming language, PHP also supports various types of operations like arithmetic operations (addition, subtraction, etc), logical operations (AND, OR etc), Increment/Decrement Operations, etc. Thus, PHP provides us with many operators to perform such operations on various operands or variables, or values. A comment in PHP code is a line that is not executed as a part of the program. Its only purpose is to be read by someone who is looking at the code. Comments can be used to: Let others understand your code. Remind yourself of what you did - Most programmers have experienced coming back to their own work a year or two later and having to re ...Display PHP errors via .htaccess configuration. Developers usually have access to the directory files. The directive for showing PHP errors can also be enabled or disabled using the .htaccess file located in the root or public directory of the project. php_flag display_startup_errors on php_flag display_errors onCreate an Array in PHP. In PHP, the array () function is used to create an array: array (); In PHP, there are three types of arrays: Indexed arrays - Arrays with a numeric index. Associative arrays - Arrays with named keys. Multidimensional arrays - Arrays containing one or more arrays.strpos () - Search For a Text Within a String. The PHP strpos () function searches for a specific text within a string. If a match is found, the function returns the character position of the first match. If no match is found, it will return FALSE.Aug 1, 2023 · The simplest way to specify a string is to enclose it in single quotes (the character ' ). To specify a literal single quote, escape it with a backslash ( \ ). To specify a literal backslash, double it ( \\ ). All other instances of backslash will be treated as a literal backslash: this means that the other escape sequences you might be used to ... Where src/ is the directory containing all your PHP code. Then, run the commands to build and run the Docker image: $ docker build -t my-php-app . $ docker run -d --name my-running-app my-php-app. We recommend that you add a php.ini configuration file; see the "Configuration" section for details.strpos () - Search For a Text Within a String. The PHP strpos () function searches for a specific text within a string. If a match is found, the function returns the character position of the first match. If no match is found, it will return FALSE. Aug 1, 2023 · PHP Installer Tools on Windows. Recommended Configuration on Windows systems. Manual PHP Installation on Windows. Building from source. Command Line PHP on Microsoft Windows. Apache 2.x on Microsoft Windows. Troubleshooting PHP on Windows. Installation on Cloud Computing platforms. Azure App Services. PHP $_GET. PHP $_GET is a PHP super global variable which is used to collect form data after submitting an HTML form with method="get". $_GET can also collect data sent in the URL. Assume we have an HTML page that contains a hyperlink with parameters:7 Min Read. PHP (Hypertext Preprocessor) is known as a general-purpose scripting language that can be utilized to create intuitive and dynamic websites. It was among the pioneer server-side language that can be integrated into HTML, making it easier to include functionality to web pages without requiring to call external data.8.1. Release Date 2021-11-25. Version Status Supported. PHP 8.1, released in 2021, brings major new features such as Enums, Fibers, never return type, Intersection Types, readonly properties, and more, while ironing out some of its undesired legacy features by deprecating them.PHP Conditional Statements. Very often when you write code, you want to perform different actions for different conditions. You can use conditional statements in your code to do this. In PHP we have the following conditional statements: if statement - executes some code if one condition is true Instagram PHP's behaviour when using more than one unparenthesized ternary operator within a single expression is non-obvious compared to other languages. Indeed prior to PHP 8.0.0, ternary expressions were evaluated left-associative, instead of right-associative like most other programming languages.PHP is an open-source, interpreted, and object-oriented scripting language that can be executed at the server-side. PHP is well suited for web development. Therefore, it is used to develop web applications (an application that executes on the server and generates the dynamic page.). PHP was created by Rasmus Lerdorf in 1994 but appeared in the ...Note that the ; is redundant; as the answers suggest this short-tag expands to an echo with a semicolon added to the end, as per the php documents. – not-just-yeti Oct 5, 2015 at 1:25
Click on the URL button, Enter URL and Submit. This tool supports loading the PHP File to beautify. Click on the Upload button and select File. It beautify pure PHP framework file such as Laravel, CodeIgniter, YII, CakePHP, Symfony and many more one file at a time. PHP Source Code Beautifier Online works well on Windows, MAC, Linux, Chrome .... Jerome
Here we would like to show the very basics of PHP in a short, simple tutorial. This text only deals with dynamic web page creation with PHP, though PHP is not only capable of creating web pages. See the section titled What can PHP do for more information. PHP-enabled web pages are treated just like regular HTML pages and you can create and edit ...在 PHP 中，赋值运算符 = 用于给变量赋值。 在 PHP 中，算术运算符 + 用于把值加在一起。 PHP 算术运算符 运算符 名称 描述 实例 结果 x + y 加 x 和 y 的和 2 + 2 4 x - y 减 x 和 y 的差 5 - 2 3 x * y 乘 x 和 y 的积 5 * 2 10 x / y 除 x 和 y 的商 15 /.. Create an Array in PHP. In PHP, the array () function is used to create an array: array (); In PHP, there are three types of arrays: Indexed arrays - Arrays with a numeric index. Associative arrays - Arrays with named keys. Multidimensional arrays - Arrays containing one or more arrays.However, PHP Manual is not listed "(" and ")" in precedence list. It looks like "(" and ")" has higher precedence as it should be. Note: If you write following code, you would need "()" to get expected value.Basic PHP Syntax. A PHP script can be placed anywhere in the document. The default file extension for PHP files is " .php ". A PHP file normally contains HTML tags, and some PHP scripting code. Below, we have an example of a simple PHP file, with a PHP script that uses a built-in PHP function " echo " to output the text "Hello World!" May 5, 2012 · In order to set project specific configuration options, simply add a php.ini file to your project, and then run the built-in server with this flag: php -S localhost:8000 -c php.ini. This is especially helpful for settings that cannot be set at runtime (ini_set ()). up. down. Required Knowledge. Before you begin this PHP tutorial, it is necessary that you have a basic understanding and experience of the following: HTML - PHP can be written with HTML, so it's essential. Basic programming knowledge - If you have any traditional programming experience like C, then learning PHP will be very easy for you.Required Knowledge. Before you begin this PHP tutorial, it is necessary that you have a basic understanding and experience of the following: HTML - PHP can be written with HTML, so it's essential. Basic programming knowledge - If you have any traditional programming experience like C, then learning PHP will be very easy for you.PHP: PHP 8.0.0 Release Announcement. PHP 8.1.23 Released! Change language: Released! PHP 8.0 is a major update of the PHP language. It contains many new features and optimizations including named arguments, union types, attributes, constructor property promotion, match expression, nullsafe operator, JIT, and improvements in the type system ...The optional timestamp parameter in the date () function specifies a timestamp. If omitted, the current date and time will be used (as in the examples above). The PHP mktime () function returns the Unix timestamp for a date. The Unix timestamp contains the number of seconds between the Unix Epoch (January 1 1970 00:00:00 GMT) and the time ... PHP Conditional Statements. Very often when you write code, you want to perform different actions for different conditions. You can use conditional statements in your code to do this. In PHP we have the following conditional statements: if statement - executes some code if one condition is true PHP: Hypertext Preprocessor. popular general-purpose scripting language that is especially suited to web development. Fast, flexible and pragmatic, PHP powers everything from your blog to the most popular websites in the world. What's new in 8.2 Download. 8.2.9 · Changelog · Upgrading.Nowadays, it's better to use queues than threads (for those who don't use Laravel there are tons of other implementations out there like this).. The basic idea is, your original PHP script puts tasks or jobs into a queue. Where src/ is the directory containing all your PHP code. Then, run the commands to build and run the Docker image: $ docker build -t my-php-app . $ docker run -d --name my-running-app my-php-app. We recommend that you add a php.ini configuration file; see the "Configuration" section for details. PHP's behaviour when using more than one unparenthesized ternary operator within a single expression is non-obvious compared to other languages. Indeed prior to PHP 8.0.0, ternary expressions were evaluated left-associative, instead of right-associative like most other programming languages. A session is started with the session_start () function. Session variables are set with the PHP global variable: $_SESSION. Now, let's create a new page called "demo_session1.php". In this page, we start a new PHP session and set some session variables:Where src/ is the directory containing all your PHP code. Then, run the commands to build and run the Docker image: $ docker build -t my-php-app . $ docker run -d --name my-running-app my-php-app. We recommend that you add a php.ini configuration file; see the "Configuration" section for details. Variables in PHP are represented by a dollar sign followed by the name of the variable. The variable name is case-sensitive. Variable names follow the same rules as other labels in PHP. A valid variable name starts with a letter or underscore, followed by any number of letters, numbers, or underscores..