Aug 1, 2023 · Description ¶. $_SERVER is an array containing information such as headers, paths, and script locations. The entries in this array are created by the web server, therefore there is no guarantee that every web server will provide any of these; servers may omit some, or provide others not listed here. However, most of these variables are ... Mar 20, 2013 · If you find that when you restart your computer, this solution will not work anymore: Set the Path like as following: Step 1 - Click on the Windows icon. Step 2 - Click on the Settings icon. Step 3 - Click on System. Step 4 - Click on About. Step 5 - Click on System info. Step 6 - Click on Advanced system settings. 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.default: code to be executed if n is different from all labels; } This is how it works: First we have a single expression n (most often a variable), that is evaluated once. The value of the expression is then compared with the values for each case in the structure. If there is a match, the block of code associated with that case is executed.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 ... 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.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.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:لغة 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 ...Aug 1, 2023 · Returns a string formatted according to the given format string using the given integer timestamp (Unix timestamp) or the current time if no timestamp is given. In other words, timestamp is optional and defaults to the value of time(). Validate Form Data With PHP. The first thing we will do is to pass all variables through PHP's htmlspecialchars () function. When we use the htmlspecialchars () function; then if a user tries to submit the following in a text field: - this would not be executed, because it would be saved as HTML escaped code, like this: This PHP tutorial, whether you’re a beginner or a professional, our tutorial is designed to provide you with in-depth knowledge of the PHP scripting language. With our PHP tutorial, you’ll learn all the important topics, including control statements, functions, arrays, strings, file handling, form handling, regular expressions, date and ...(php 4, php 5, php 7, php 8) elseif , as its name suggests, is a combination of if and else . Like else , it extends an if statement to execute a different statement in case the original if expression evaluates to false .Try it Yourself ». Code explanation: First, check if the input field is empty (str.length == 0). If it is, clear the content of the txtHint placeholder and exit the function. However, if the input field is not empty, do the following: Create an XMLHttpRequest object. Create the function to be executed when the server response is ready.Php 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.Aug 1, 2023 · Returns a string formatted according to the given format string using the given integer timestamp (Unix timestamp) or the current time if no timestamp is given. In other words, timestamp is optional and defaults to the value of time(). I run 'php artisan migrate' command on window 8.1, laravel 7, xamp (php version 7.3.2) . I found some error, my all table did not migrate, how to fix [closed] Illuminate\Database\QueryException SQLSTATE [42S01]: Base table or view already exists: 1050 Table 'users' already exists. I have a CLI screenshot of the error:Aug 1, 2023 · 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. 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 ...Great if you like your tutorials to the point. 11. Learn-php.org Free Interactive PHP Tutorial. Learn-php.org free interactive PHP tutorial. The unique thing about this PHP tutorial is that it’s a set of interactive exercises that encourage you to try out coding and see if you can get the expected output.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 · Herramientas de instalación de PHP en Windows; Configuración recomendada en sistemas Windows; Instalación manual de PHP en Windows; Compilando desde código fuente; Línea de comandos PHP en Microsoft Windows; Apache 2.x en Microsoft Windows; Resolución de problemas de PHP en Windows; Instalación en las plataformas de Nube Informática ... A PHP framework is a platform to create PHP web applications. PHP frameworks provide code libraries for commonly used functions, cutting down on the amount of original code you need to write. There are many good reasons for using PHP frameworks as opposed to coding from scratch. Because PHP frameworks have built-in libraries and tools, the time ...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 ...Validate Form Data With PHP. The first thing we will do is to pass all variables through PHP's htmlspecialchars () function. When we use the htmlspecialchars () function; then if a user tries to submit the following in a text field: - this would not be executed, because it would be saved as HTML escaped code, like this: Grav 1.7.29 PHP 8.1 benchmark results: 2137.43 req/sec 🏆; PHP 8.1 is the undisputed winner with Grav, closely followed by PHP 8.0 and the rest. Being a relatively new CMS, it has a smaller market share than WordPress. Hence, it can drop support for older PHP versions quite quickly. That’s one of the most significant advantages of modern CMSs.PHP Version: 4+ PHP Changelog: PHP 7.2: The headers parameter also accepts an array PHP 5.4: Added header injection protection for the headers parameter. PHP 4.3.0: (Windows only) All custom headers (like From, Cc, Bcc and Date) are supported, and are not case-sensitive. PHP 4.2.3: The parameter parameter is disabled in safe mode Herramientas de instalación de PHP en Windows; Configuración recomendada en sistemas Windows; Instalación manual de PHP en Windows; Compilando desde código fuente; Línea de comandos PHP en Microsoft Windows; Apache 2.x en Microsoft Windows; Resolución de problemas de PHP en Windows; Instalación en las plataformas de Nube Informática ...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 ...MySQL is a database system used on the web. MySQL is a database system that runs on a server. MySQL is ideal for both small and large applications. MySQL is very fast, reliable, and easy to use. MySQL uses standard SQL. MySQL compiles on a number of platforms. MySQL is free to download and use. MySQL is developed, distributed, and supported by ...Aug 1, 2023 · 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 . Aug 1, 2023 · PHP tags. When PHP parses a file, it looks for opening and closing tags, which are <?php and ?> which tell PHP to start and stop interpreting the code between them. . Parsing in this manner allows PHP to be embedded in all sorts of different documents, as everything outside of a pair of opening and closing tags is ignored by the PHP par The best IDE for PHP in my opinion is Zend Studio (which itself is based on Eclipse PDT). Note that in this case "best" does not necessarily mean "good." It is slow and a bit buggy, but even so, it's still the best option for PHP programmers. I've tried a ton of PHP editors over the years and I haven't yet found one that works great.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 ...The best IDE for PHP in my opinion is Zend Studio (which itself is based on Eclipse PDT). Note that in this case "best" does not necessarily mean "good." It is slow and a bit buggy, but even so, it's still the best option for PHP programmers. I've tried a ton of PHP editors over the years and I haven't yet found one that works great.www.php.net – PHP distribution, tutorials, newsgroups, and more. www.phpfreaks.com - PHP and MySQL tutorials, scripts, forums, and more. www.phpbuilder.com – Collection of PHP resources. Hello World If your web server supports PHP, type this example into a text file called hello.php and access it in your browser by Well organized and easy to understand Web building tutorials with lots of examples of how to use HTML, CSS, JavaScript, SQL, Python, PHP, Bootstrap, Java, XML and more.Sep 28, 2020 · A PHP framework is a platform to create PHP web applications. PHP frameworks provide code libraries for commonly used functions, cutting down on the amount of original code you need to write. There are many good reasons for using PHP frameworks as opposed to coding from scratch. Because PHP frameworks have built-in libraries and tools, the time ... Aug 1, 2023 · Herramientas de instalación de PHP en Windows; Configuración recomendada en sistemas Windows; Instalación manual de PHP en Windows; Compilando desde código fuente; Línea de comandos PHP en Microsoft Windows; Apache 2.x en Microsoft Windows; Resolución de problemas de PHP en Windows; Instalación en las plataformas de Nube Informática ... 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 ...15. According to the article How to Get Current Datetime (NOW) with PHP, there are two common ways to get the current date. To get current datetime (now) with PHP, you can use the date class with any PHP version, or better the datetime class with PHP >= 5.2. Various date format expressions are available here.(php 4, php 5, php 7, php 8) elseif , as its name suggests, is a combination of if and else . Like else , it extends an if statement to execute a different statement in case the original if expression evaluates to false .If you have permission to SSH into the remote server, use the command line to check the installed PHP version. This method is also useful for checking the PHP version installed locally. 1. Type the PHP command: php -v. 2. The php -v command works on Linux, macOS, Windows, and other supported systems. Its output contains the PHP version number ...Tutorial PHP #01: Mengenal Bahasa Pemrograman PHP. Tutorial PHP #02: Persiapan Pemrograman PHP di Linux. Tutorial PHP #02: Persiapan Pemrograman PHP di Linux dengan XAMPP. Tutorial PHP #02: Persiapan Pemrograman PHP di Windows. Tutorial PHP #03: Memahami Struktur Dasar Sintaks PHP. Tutorial PHP #04: Mengenal Fungsi untuk Mencetak Teks.Also, you can increase PHP’s memory limit for specific websites. One method would be to place a php.ini file in the site’s webroot. You can even set the limit for specific scriptname.php. For example using ini_set(‘memory_limit’,’256MB’). How to increase PHP memory_limit. To increase the PHP memory limit setting, edit your PHP.ini file.15. According to the article How to Get Current Datetime (NOW) with PHP, there are two common ways to get the current date. To get current datetime (now) with PHP, you can use the date class with any PHP version, or better the datetime class with PHP >= 5.2. Various date format expressions are available here.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.May 17, 2023 · PHP is a script on the server-side used for the creation of Static or Dynamic Web sites or Web applications. PHP is a pre-processor for hypertext, which used to stand for home pages. The software used to build web applications is an open-source, server-side scripting language. We say a program designed for automated work by writing a script ... You can also call the script from the command line after chmod'ing the file (ie: chmod 755 file.php). On your first line of the file, enter "#!/usr/bin/php" (or to wherever your php executable is located). If you want to suppress the PHP headers, use the line of "#!/usr/bin/php -q" for your path. up. down.This PHP tutorial, whether you’re a beginner or a professional, our tutorial is designed to provide you with in-depth knowledge of the PHP scripting language. With our PHP tutorial, you’ll learn all the important topics, including control statements, functions, arrays, strings, file handling, form handling, regular expressions, date and ...PHP Version: 4+ PHP Changelog: PHP 7.2: The headers parameter also accepts an array PHP 5.4: Added header injection protection for the headers parameter. PHP 4.3.0: (Windows only) All custom headers (like From, Cc, Bcc and Date) are supported, and are not case-sensitive. PHP 4.2.3: The parameter parameter is disabled in safe mode Jan 14, 2021 · If you have permission to SSH into the remote server, use the command line to check the installed PHP version. This method is also useful for checking the PHP version installed locally. 1. Type the PHP command: php -v. 2. The php -v command works on Linux, macOS, Windows, and other supported systems. Its output contains the PHP version number ... PHP User Defined Functions. Besides the built-in PHP functions, it is possible to create your own functions. A function is a block of statements that can be used repeatedly in a program. A function will not execute automatically when a page loads. A function will be executed by a call to the function.Description ¶. $_SERVER is an array containing information such as headers, paths, and script locations. The entries in this array are created by the web server, therefore there is no guarantee that every web server will provide any of these; servers may omit some, or provide others not listed here. However, most of these variables are ...May 29, 2023 · Factors to Consider When Choosing a PHP Framework. Best PHP Frameworks in 2023 (Comparison Table) 10 Best PHP Frameworks in 2023 (Ranked) Laravel. Symfony. Yii 2. CakePHP. CodeIgniter. Zend Framework. Well organized and easy to understand Web building tutorials with lots of examples of how to use HTML, CSS, JavaScript, SQL, Python, PHP, Bootstrap, Java, XML and more. Mar 20, 2013 · If you find that when you restart your computer, this solution will not work anymore: Set the Path like as following: Step 1 - Click on the Windows icon. Step 2 - Click on the Settings icon. Step 3 - Click on System. Step 4 - Click on About. Step 5 - Click on System info. Step 6 - Click on Advanced system settings. 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 ... 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 ... 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.Aug 1, 2023 · Description ¶. $_SERVER is an array containing information such as headers, paths, and script locations. The entries in this array are created by the web server, therefore there is no guarantee that every web server will provide any of these; servers may omit some, or provide others not listed here. However, most of these variables are ... 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.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 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. default: code to be executed if n is different from all labels; } This is how it works: First we have a single expression n (most often a variable), that is evaluated once. The value of the expression is then compared with the values for each case in the structure. If there is a match, the block of code associated with that case is executed.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: 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-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 .Assignment Operators. ¶. The basic assignment operator is "=". Your first inclination might be to think of this as "equal to". Don't. It really means that the left operand gets set to the value of the expression on the right (that is, "gets set to"). The value of an assignment expression is the value assigned.Dec 8, 2021 · 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. 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 Microsoft SQL Server. PHP is pleasingly zippy in its execution ...Try it Yourself ». Code explanation: First, check if the input field is empty (str.length == 0). If it is, clear the content of the txtHint placeholder and exit the function. However, if the input field is not empty, do the following: Create an XMLHttpRequest object. Create the function to be executed when the server response is ready.Jan 22, 2009 · 15. According to the article How to Get Current Datetime (NOW) with PHP, there are two common ways to get the current date. To get current datetime (now) with PHP, you can use the date class with any PHP version, or better the datetime class with PHP >= 5.2. Various date format expressions are available here. PHP Operators. Operators are used to perform operations on variables and values. PHP divides the operators in the following groups: Arithmetic operators. Assignment operators. Comparison operators. Increment/Decrement operators. Logical operators. String operators.I run 'php artisan migrate' command on window 8.1, laravel 7, xamp (php version 7.3.2) . I found some error, my all table did not migrate, how to fix [closed] Illuminate\Database\QueryException SQLSTATE [42S01]: Base table or view already exists: 1050 Table 'users' already exists. I have a CLI screenshot of the error: MySQL is a database system used on the web. MySQL is a database system that runs on a server. MySQL is ideal for both small and large applications. MySQL is very fast, reliable, and easy to use. MySQL uses standard SQL. MySQL compiles on a number of platforms. MySQL is free to download and use. MySQL is developed, distributed, and supported by ...PHP User Defined Functions. Besides the built-in PHP functions, it is possible to create your own functions. A function is a block of statements that can be used repeatedly in a program. A function will not execute automatically when a page loads. A function will be executed by a call to the function.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 ...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 .Apr 24, 2023 · PHP is a server-side scripting language, which means that a server executes the instructions in a script. Then, the server provides data on request, channels the requests, and organizes the information in a database. When a web server receives a script, it will process the request and send output to a web browser in an HTML format. In this tutorial, you’ll create a user registration form that consists of the following input fields: Username. Email. Password. Password confirmation. Agreement checkbox. Register button. When a user fills out the form and click the Register button, you need to: Sanitize & validate the user inputs.
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. . Old country bbq pits buc ee
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 ...Aug 1, 2023 · 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. To change the PHP settings, open your User or Workspace Settings ( ⌘, (Windows, Linux Ctrl+,)) and type 'php' to filter the list of available settings. To set the PHP executable path, select the Edit in settings.json link under PHP > Validate: Executable Path, which will open your user settings.json file. Select and Filter Data From a MySQL Database. The WHERE clause is used to filter records. The WHERE clause is used to extract only those records that fulfill a specified condition. SELECT column_name (s) FROM table_name WHERE column_name operator value. To learn more about SQL, please visit our SQL tutorial.InstagramUse W3Schools Spaces to build, test and deploy code. The code editor lets you write and practice different types of computer languages. It includes PHP, but you can use it for other languages too. New languages are added all the time: Learn More. 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:PHP is a script on the server-side used for the creation of Static or Dynamic Web sites or Web applications. PHP is a pre-processor for hypertext, which used to stand for home pages. The software used to build web applications is an open-source, server-side scripting language. We say a program designed for automated work by writing a script ...Returns a string formatted according to the given format string using the given integer timestamp (Unix timestamp) or the current time if no timestamp is given. In other words, timestamp is optional and defaults to the value of time().Aug 1, 2023 · The reason for the two different variations of "and" and "or" operators is that they operate at different precedences. (See Operator Precedence.) 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. 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 frameworks offer several benefits, making them a compelling choice for web developers. Firstly, PHP frameworks offer a structured approach to development with pre-built components, streamlining the process, accelerating project completion, and enhancing productivity. Secondly, using a PHP framework can contribute to cost savings.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 ...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 ....