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PHP Syntax And Semantics
The syntax and semantics of PHP, a programming language, form a set of rules that define how a PHP program can be written and interpreted. Overview Historically, the development of PHP has been somewhat haphazard. To counter this, the PHP Framework Interop Group (FIG) has created The PHP Standards Recommendation (PSR) documents that have helped bring more standardization to the language since 2009. The modern coding standards are contained in PSR-1 (Basic Coding Standard) and PSR-2 (Coding Style Guide). Keywords Some keywords represent things that look like functions, some look like constants, but they are actually language constructs. It is forbidden to use any keywords as constants, class names, functions or methods. Using them as variable names is allowed, but it can be confusing. *__halt_compiler() *abstract *and *array() *as *break *callable (as of PHP 5.4) *case *catch *class *clone *const *continue *declare *default *die() *do *echo *else *elseif ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Syntax (programming Languages)
In computer science, the syntax of a computer language is the rules that define the combinations of symbols that are considered to be correctly structured Statement (computer science), statements or Expression (computer science), expressions in that language. This applies both to programming languages, where the document represents source code, and to markup languages, where the document represents data. The syntax of a language defines its surface form. Text-based user interface, Text-based computer languages are based on sequences of Character (computing), characters, while visual programming languages are based on the spatial layout and connections between symbols (which may be textual or graphical). Documents that are syntactically invalid are said to have a syntax error. When designing the syntax of a language, a designer might start by writing down examples of both legal and illegal String (computer science), strings, before trying to figure out the general rules from these ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Binary File
A binary file is a computer file that is not a text file. The term "binary file" is often used as a term meaning "non-text file". Many binary file formats contain parts that can be interpreted as text; for example, some computer document files containing formatted text, such as older Microsoft Word document files, contain the text of the document but also contain formatting information in binary form. Background and terminology All modern computers store information in the form of bits (binary digits), using binary code. For this reason, all data stored on a computer is, in some sense, "binary". However, one particularly useful and ubiquitous type of data stored on a computer is one in which the bits represent text, by way of a character encoding. Those files are called " text files" and files which are not like that are referred to as "binary files", as a sort of retronym or hypernym. Some "text files" contain portions that are actually binary data, and many "binary fil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Curly Brackets
A bracket is either of two tall fore- or back-facing punctuation marks commonly used to isolate a segment of text or data from its surroundings. They come in four main pairs of shapes, as given in the box to the right, which also gives their names, that vary between British and American English. "Brackets", without further qualification, are in British English the ... marks and in American English the ... marks. Other symbols are repurposed as brackets in specialist contexts, such as those used by linguists. Brackets are typically deployed in symmetric pairs, and an individual bracket may be identified as a "left" or "right" bracket or, alternatively, an "opening bracket" or "closing bracket", respectively, depending on the directionality of the context. In casual writing and in technical fields such as computing or linguistic analysis of grammar, brackets nest, with segments of bracketed material containing embedded within them other further bracketed sub-segments. The num ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Associative Array
In computer science, an associative array, key-value store, map, symbol table, or dictionary is an abstract data type that stores a collection of (key, value) pairs, such that each possible key appears at most once in the collection. In mathematical terms, an associative array is a function with ''finite'' domain. It supports 'lookup', 'remove', and 'insert' operations. The dictionary problem is the classic problem of designing efficient data structures that implement associative arrays. The two major solutions to the dictionary problem are hash tables and search trees..Dietzfelbinger, M., Karlin, A., Mehlhorn, K., Meyer auf der Heide, F., Rohnert, H., and Tarjan, R. E. 1994"Dynamic Perfect Hashing: Upper and Lower Bounds". SIAM J. Comput. 23, 4 (Aug. 1994), 738-761. http://portal.acm.org/citation.cfm?id=182370 It is sometimes also possible to solve the problem using directly addressed arrays, binary search trees, or other more specialized structures. Many programmin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Square Brackets
A bracket is either of two tall fore- or back-facing punctuation marks commonly used to isolate a segment of text or data from its surroundings. They come in four main pairs of shapes, as given in the box to the right, which also gives their names, that vary between British and American English. "Brackets", without further qualification, are in British English the ... marks and in American English the ... marks. Other symbols are repurposed as brackets in specialist contexts, such as those used by linguists. Brackets are typically deployed in symmetric pairs, and an individual bracket may be identified as a "left" or "right" bracket or, alternatively, an "opening bracket" or "closing bracket", respectively, depending on the directionality of the context. In casual writing and in technical fields such as computing or linguistic analysis of grammar, brackets nest, with segments of bracketed material containing embedded within them other further bracketed sub-segments. The nu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Concatenation
In formal language theory and computer programming, string concatenation is the operation of joining character strings end-to-end. For example, the concatenation of "snow" and "ball" is "snowball". In certain formalizations of concatenation theory, also called string theory, string concatenation is a primitive notion. Syntax In many programming languages, string concatenation is a binary infix operator, and in some it is written without an operator. This is implemented in different ways: * Overloading the plus sign + Example from C#: "Hello, " + "World" has the value "Hello, World". * Dedicated operator, such as . in PHP, & in Visual Basic, and , , in SQL. This has the advantage over reusing + that it allows implicit type conversion to string. * string literal concatenation, which means that adjacent strings are concatenated without any operator. Example from C: "Hello, " "World" has the value "Hello, World". In many scientific publications or standards the con ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Free-form Language
In computer programming, a free-form language is a programming language in which the positioning of characters on the page in program text is insignificant. Program text does not need to be placed in specific columns as on old punched card systems, and frequently ends of lines are insignificant. Whitespace characters are used only to delimit tokens, and have no other significance. Free-form languages allow a greater degree of flexibility and have fewer syntactic rules to learn, which could lower the entry barrier for beginners. Most free-form languages descend from ALGOL, including C, Pascal, and Perl. Lisp languages are free-form, although they do not descend from ALGOL. Rexx and its dialects ooRexx and NetRexx are mostly free-form, though in some cases whitespace characters are concatenation operators. SQL, though not a full programming language, is also free-form. Most free-form languages are also structured programming languages, which is sometimes thought to go along wi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Whitespace (computer Science)
A whitespace character is a character data element that represents white space when text is rendered for display by a computer. For example, a ''space'' character (, ASCII 32) represents blank space such as a word divider in a Western script. A printable character results in output when rendered, but a whitespace character does not. Instead, whitespace characters define the layout of text to a limited degree, interrupting the normal sequence of rendering characters next to each other. The output of subsequent characters is typically shifted to the right (or to the left for right-to-left script) or to the start of the next line. The effect of multiple sequential whitespace characters is cumulative such that the next printable character is rendered at a location based on the accumulated effect of preceding whitespace characters. The origin of the term ''whitespace'' is rooted in the common practice of rendering text on white paper. Normally, a whitespace character is ''n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Newline
A newline (frequently called line ending, end of line (EOL), next line (NEL) or line break) is a control character or sequence of control characters in character encoding specifications such as ASCII, EBCDIC, Unicode, etc. This character, or a sequence of characters, is used to signify the end of a line (text file), line of text and the start of a new one. History In the mid-1800s, long before the advent of teleprinters and teletype machines, Morse code operators or telegraphists invented and used Prosigns for Morse code, Morse code prosigns to encode white space text formatting in formal written text messages. In particular, the International Morse code, Morse prosign (mnemonic break text), represented by the concatenation of literal textual Morse codes "B" and "T" characters, sent without the normal inter-character spacing, is used in Morse code to encode and indicate a ''new line'' or ''new section'' in a formal text message. Later, in the age of modern teleprinters, st ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Type Conversion
In computer science, type conversion, type casting, type coercion, and type juggling are different ways of changing an expression from one data type to another. An example would be the conversion of an integer value into a floating point value or its textual representation as a string, and vice versa. Type conversions can take advantage of certain features of type hierarchies or data representations. Two important aspects of a type conversion are whether it happens ''implicitly'' (automatically) or ''explicitly'', and whether the underlying data representation is converted from one representation into another, or a given representation is merely ''reinterpreted'' as the representation of another data type. In general, both primitive and compound data types can be converted. Each programming language has its own rules on how types can be converted. Languages with strong typing typically do little implicit conversion and discourage the reinterpretation of representations, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heredoc
In computing, a here document (here-document, here-text, heredoc, hereis, here-string or here-script) is a file literal or input stream literal: it is a section of a source code file that is treated as if it were a separate file. The term is also used for a form of multiline string literals that use similar syntax, preserving line breaks and other whitespace (including indentation) in the text. Here documents originate in the Unix shell, and are found in the Bourne shell since 1979, and most subsequent shells. Here document-style string literals are found in various high-level languages, notably the Perl programming language (syntax inspired by Unix shell) and languages influenced by Perl, such as PHP and Ruby. JavaScript also supports this functionality via template literals, a feature added in its 6th revision ( ES6). Other high-level languages such as Python, Julia and Tcl have other facilities for multiline strings. Here documents can be treated either as files or strings ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Primitive Type
In computer science, primitive data types are a set of basic data types from which all other data types are constructed. Specifically it often refers to the limited set of data representations in use by a particular processor, which all compiled programs must use. Most processors support a similar set of primitive data types, although the specific representations vary. More generally, ''primitive data types'' may refer to the standard data types built into a programming language (built-in types). Data types which are not primitive are referred to as ''derived'' or ''composite''. Primitive types are almost always value types, but composite types may also be value types. Common primitive data types The most common primitive types are those used and supported by computer hardware, such as integers of various sizes, floating-point numbers, and Boolean logical values. Operations on such types are usually quite efficient. Primitive data types which are native to the processor have a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
