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null a (or an empty element in the row) a: 1 a true a: 0 a false a: ... null.string null.symbol null.blob null.clob null.struct ... ^ PHP will unserialize any ...
PHP supports two special types: null, resource. The null data type represents a variable that has no value. The only value in the null data type is NULL. The NULL constant is not case sensitive. [30] Variables of the "resource" type represent references to resources from external sources. These are typically created by functions from a ...
The ability to represent a null character does not always mean the resulting string will be correctly interpreted, as many programs will consider the null to be the end of the string. Thus the ability to type it (in case of unchecked user input) creates a vulnerability known as null byte injection and can lead to security exploits. [10]
In object-oriented computer programming, a null object is an object with no referenced value or with defined neutral (null) behavior.The null object design pattern, which describes the uses of such objects and their behavior (or lack thereof), was first published as "Void Value" [1] and later in the Pattern Languages of Program Design book series as "Null Object".
Null-terminated strings require that the encoding does not use a zero byte (0x00) anywhere; therefore it is not possible to store every possible ASCII or UTF-8 string. [ 8 ] [ 9 ] [ 10 ] However, it is common to store the subset of ASCII or UTF-8 – every character except NUL – in null-terminated strings.
Null symbol may refer to: Null character, U+0000 <control-0000>, U+2400 ␀ SYMBOL FOR NULL (a single-character glyph "NUL") Null sign (∅), the empty set; Null (SQL) (ω), a special marker and keyword NULL in SQL; Empty string (λ, Λ, or ε), in formal language theory
Also, 0 is a standard way to refer to a null pointer in code. [90] In databases, it is possible for a field not to have a value. It is then said to have a null value. [91] For numeric fields it is not the value zero. For text fields this is not blank nor the empty string. The presence of null values leads to three-valued logic.
COBOL uses the STRING statement to concatenate string variables. MATLAB and Octave use the syntax "[x y]" to concatenate x and y. Visual Basic and Visual Basic .NET can also use the "+" sign but at the risk of ambiguity if a string representing a number and a number are together. Microsoft Excel allows both "&" and the function "=CONCATENATE(X,Y)".