PHP array introduction _ PHP Tutorial

PHP array introduction. PHP array introduction: In php, the subscript of an array can be an integer or a string in php. the element sequence of the array is not determined by the subscript, it is determined by the order in which the PHP array is introduced.
Array basics:

In php, the subscript of an array can be an integer or a string.

In php, the element sequence of an array is not determined by the subscript, but by the order in which it is "added ".

Definition:

$ Arr1 = array (element 1, element 2 ,......);

Array (1, 1.1, 5, 'ABC', true, false); // any data can be stored, which is the default subscript.

Array (2 => 1.1 =>, 3 => 5, 7 => 'ABC', 0 => true); // The subscript can be set at will (no order required, no consecutive)

Array (2 => 1, 1.1, 1 => 5, 'ABC', 0 => true); // you can add subscript or not, the Default subscript is used if no subscript is added.

// Default subscript rule: the maximum number of subscripts that have been used earlier + 1

// The subscript of this number is: 2, 3, 0

Array (2 => 1, 'DD' => 5, 1 => 1.1, 'ABC', 0 => true); // mixed subscript, also follows the Default subscript rules

Array (-2 => 1, 'DD' => 5, 1.1, 'ABC', true); // negative subscript is not included in the integer subscript, but only used as the character subscript

// The subscript of the last three items in the array is: 0, 1, 2

Array (2.7 => 1, 'DD' => 5, 1 => 1.1, 'ABC', true); // The floating point subscript is automatically converted to an integer, and the fractional part is directly removed.

Array ("2.7" => 1, 'DD' => 5, "11" => 1.1, 'ABC', true); // A numeric string subscript.

Array (2 => 1, 'DD' => 5, true => 1.1, 'ABC', false => true); // use a Boolean value as a subscript, true is 1, false is 0

Array (2 => 1, 'DD' => 5, 2 => 1.1, 'ABC', true); // if the subscript already exists, it simply overwrites the value of the submark with the same name.

Other forms:

$ Arr1 [] = 1;

$ Arr1 [] = 5;

$ Arr1 [] = 1.1;

... // Use [] directly after the variable to form an array and assign values in turn.

$ Arr2 ['A'] = 1;

$ Arr2 ['BB'] = 5;

$ Arr2 [5] = 1.1;

The subscript written in the form of... // is almost the same as the array syntax structure.

Array Category:

Key-value relationships are divided:

Associated array: an array that uses a subscript as a string and can generally express the meaning of data.

Example: $ person = array ("name" => "poe", "age" => 18, "edu" => "");

Index array: it usually refers to the continuous numeric subscript of an array whose subscript Strictly starts from 0-similar to that of a js array.

From the array level:

One-dimensional array: each element value in an array is a common value (non-array value)

Example: $ person = array ("name" => "poe", "age" => 18, "edu" => "");

Two-dimensional array: each item in an array is a one-dimensional array.

$ Person = array (

"Name" => array ("xiaohua", "xiaofang ),

"Age" => array (18, 22 ),

"Edu" => array ("graduated from college", "Elementary School ",)

);

Multi-dimensional array: and so on...

General syntax of multi-dimensional arrays:

$ V1 = array name [subscript] [subscript] [...]

Array traversal:

Basic traversal syntax:

Foreach ($ arr as [$ key =>] $ value ){

// All possible operations on $ key and $ value can be performed here-because they are a variable

// $ Key indicates the subscript of each element obtained, which may be a number or a string.

// $ Value indicates the value of each element, which may be of various types.

// This loop structure will traverse from the first entry of the array to the last entry, and then end

}

Array pointer and traversal principle:

Each array has a "pointer" inside it, which determines the elements obtained when the current value of the array is

In the foreach traversal process, the pointer is used.

Example: $ arr1 = array (2 => 1, 'DD' => 5, 1 => 1.1, 'ABC', 0 => true );

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In addition to the foreach loop location setting, pointers also depend on pointers:

1: $ v1 = current ($ arr1); // gets the value of the element pointed to by the current pointer in $ arr1. if it does not point to the element, it is false.

2: $ v1 = key ($ arr1); // Obtain the subscript of the element pointed to by the current pointer in $ arr1 ,.............

3: $ v1 = next ($ arr1); // move the pointer to the next element and obtain the value of the next element.

4: $ v1 = prev ($ arr1); // move the pointer to "previous element" and then obtain the value of the previous element.

5: $ v1 = reset ($ arr1); // move the pointer to "first element" and obtain the value of this element.

6: $ v1 = end ($ arr1); // move the pointer to the "last element" and obtain the value of this element.

7: $ v1 = each ($ arr1); // Obtain the subscript and value of the current element, and move the pointer to the next position.

Basics of arrays: In php, the subscript of an array can be an integer or a string in php. the element sequence of an array is determined not by the subscript, but by the order in which it is added...