Tutorial by Examples: t

To remove an element inside an array, e.g. the element with the index 1. $fruit = array("bananas", "apples", "peaches"); unset($fruit[1]); This will remove the apples from the list, but notice that unset does not change the indexes of the remaining elements. So $fr...

A cookie is set using the setcookie() function. Since cookies are part of the HTTP header, you must set any cookies before sending any output to the browser. Example: setcookie("user", "Tom", time() + 86400, "/"); // check syntax for function params Description: ...

Retrieve and Output a Cookie Named user The value of a cookie can be retrieved using the global variable $_COOKIE. example if we have a cookie named user we can retrieve it like this echo $_COOKIE['user'];

Use the isset() function upon the superglobal $_COOKIE variable to check if a cookie is set. Example: // PHP <7.0 if (isset($_COOKIE['user'])) { // true, cookie is set echo 'User is ' . $_COOKIE['user']; else { // false, cookie is not set echo 'User is not logged in'; } ...

var='0123456789abcdef' # Define a zero-based offset $ printf '%s\n' "${var:3}" 3456789abcdef # Offset and length of substring $ printf '%s\n' "${var:3:4}" 3456 4.2 # Negative length counts from the end of the string $ printf '%s\n' "${var:3:-5}" 3456789a...

cat < file.txt Output is same as cat file.txt, but it reads the contents of the file from standard input instead of directly from the file. printf "first line\nSecond line\n" | cat -n The echo command before | outputs two lines. The cat command acts on the output to add line num...

# Length of a string $ var='12345' $ echo "${#var}" 5 Note that it's the length in number of characters which is not necessarily the same as the number of bytes (like in UTF-8 where most characters are encoded in more than one byte), nor the number of glyphs/graphemes (some of which ...

One of the most common tasks is retrieving an existing element from the DOM to manipulate. Most commonly these methods are executed on document, because it is the root node, but all these methods work on any HTML element in the tree. They will only return children from the node it is executed on. R...

An element can be cloned by invoking the cloneNode method on it. If the first parameter passed to cloneNode is true, the children of the original will also be cloned. var original = document.getElementsByTagName("li")[0]; var clone = original.cloneNode(true);

CREATE TABLE Employees ( Id int NOT NULL, PRIMARY KEY (Id), ... ); This will create the Employees table with 'Id' as its primary key. The primary key can be used to uniquely identify the rows of a table. Only one primary key is allowed per table. A key can also be composed by one...

Many databases allow to make the primary key value automatically increment when a new key is added. This ensures that every key is different. MySQL CREATE TABLE Employees ( Id int NOT NULL AUTO_INCREMENT, PRIMARY KEY (Id) ); PostgreSQL CREATE TABLE Employees ( Id SERIAL PRIMARY...

This will draw a line at the bottom of every view but the last to act as a separator between items. public class SeparatorDecoration extends RecyclerView.ItemDecoration { private final Paint mPaint; private final int mAlpha; public SeparatorDecoration(@ColorInt int color, float w...

Classes/structs can have inheritance relations. If a class/struct B inherits from a class/struct A, this means that B has as a parent A. We say that B is a derived class/struct from A, and A is the base class/struct. struct A { public: int p1; protected: int p2; private: int p3;...

When using inheritance, you can specify the virtual keyword: struct A{}; struct B: public virtual A{}; When class B has virtual base A it means that A will reside in most derived class of inheritance tree, and thus that most derived class is also responsible for initializing that virtual base: ...

Aside from single inheritance: class A {}; class B : public A {}; You can also have multiple inheritance: class A {}; class B {}; class C : public A, public B {}; C will now have inherit from A and B at the same time. Note: this can lead to ambiguity if the same names are used in multipl...

The class template std::shared_ptr defines a shared pointer that is able to share ownership of an object with other shared pointers. This contrasts to std::unique_ptr which represents exclusive ownership. The sharing behavior is implemented through a technique known as reference counting, where the...

Instances of std::weak_ptr can point to objects owned by instances of std::shared_ptr while only becoming temporary owners themselves. This means that weak pointers do not alter the object's reference count and therefore do not prevent an object's deletion if all of the object's shared pointers are ...

Function overloading is having multiple functions declared in the same scope with the exact same name exist in the same place (known as scope) differing only in their signature, meaning the arguments they accept. Suppose you are writing a series of functions for generalized printing capabilities, b...

A std::vector can be initialized in several ways while declaring it: C++11 std::vector<int> v{ 1, 2, 3 }; // v becomes {1, 2, 3} // Different from std::vector<int> v(3, 6) std::vector<int> v{ 3, 6 }; // v becomes {3, 6} // Different from std::vector<int> v{3, ...

Appending an element at the end of a vector (by copying/moving): struct Point { double x, y; Point(double x, double y) : x(x), y(y) {} }; std::vector<Point> v; Point p(10.0, 2.0); v.push_back(p); // p is copied into the vector. C++11 Appending an element at the end of a vector ...