Php Getting Started Tutorial array operation tutorial

Source: Internet
Author: User
Tags arrays numeric php tutorial shuffle

What is an array?
When using PHP for development, you need to create many similar variables either early or late.

Without many similar variables, you can store data as elements in an array.

All elements in the array have their own IDs, so they can be easily accessed.

There are three types of arrays:
Numeric array
Array with digit ID key
Join array
Each ID key in the array is associated with a value.
Multi-dimensional array
Array Value array that contains one or more arrays
Each element stored in the value array has a digital ID key.

You can use different methods to create a numeric array:

Example 1
In this example, the ID key is automatically assigned:

$ Names = array ("Peter", "Quagmire", "Joe"); Example 2
In this example, we manually allocate the ID key:

$ Names [0] = "Peter ";
$ Names [1] = "Quagmire ";
$ Names [2] = "Joe ";
You can use these ID keys in the script:

<? Php Tutorial

$ Names [0] = "Peter ";
$ Names [1] = "Quagmire ";
$ Names [2] = "Joe ";

Echo $ names [1]. "and". $ names [2]. "are". $ names [0]. "'s neighbors ";
?>
Output of the above code:

Quagmire and Joe are Peter's neighbors associated array
Join array. Each ID key is associated with a value.

It is not the best practice to use a numeric array to store data related to specific named values.

By associating arrays, we can use values as keys and assign values to them.

Example 1
In this example, we use an array to allocate ages to different people:

$ Ages = array ("Peter" => 32, "Quagmire" => 30, "Joe" => 34); Example 2
This example is the same as example 1, but shows another method to create an array:

$ Ages ['Peter '] = "32 ";
$ Ages ['quagmire'] = "30 ";
$ Ages ['job'] = "34 ";
You can use the ID key in the script:

<? Php

$ Ages ['Peter '] = "32 ";
$ Ages ['quagmire'] = "30 ";
$ Ages ['job'] = "34 ";

Echo "Peter is". $ ages ['Peter ']. "years old .";
?>
Output of the above script:

Peter is 32 years old. Multi-dimensional array
In a multi-dimensional array, each element in the main array is also an array. Each element in the sub-array can also be an array, and so on.

Example 1
In this example, we create a multidimensional array with an automatically assigned ID key:

$ Families = array
(
"Griffin in" => array
  (
"Peter ",
"Lois ",
"Megan"
),
"Quagmire" => array
  (
"Glenn"
),
"Brown" => array
  (
"Cleveland ",
"Loretta ",
"Junior"
  )
);
If this array is output, it should be similar to the following:

Array
(
[Griffin in] => Array
  (
[0] => Peter
[1] => Lois
[2] => Megan
  )
[Quagmire] => Array
  (
[0] => Glenn
  )
[Brown] => Array
  (
[0] => Cleveland
[1] => Loretta
[2] => Junior
  )
)
Example 2
Let's try to display a single value in the above array:

Echo "Is". $ families ['grigging'] [2].
"A part of the Griffin family? ";
Output of the above code:

Is Megan a part of the Griffin family?

Add element to array
Php is a weak language. Therefore, you do not need to declare the length for the php array like the C language. The process of adding elements to it is also a process of declaration and initialization.
The code is as follows:
$ Capitals = array (
'Babama' => 'mongomery ',
'Apache' => 'juneau ',
'Arizona '=> 'Phoenix'
);

It's easy to add more elements.
The code is as follows:
$ Capitals ['Arkansas '] = 'Little Rock ';

You can use the array_push () and array_unshift () functions to add elements to arrays that are not associated with arrays but numeric indexes.
2. Delete elements from array
You can use the unset () function to remove elements from an array.
The code is as follows:
Unset ($ capitals ['California ']);

You can also use the array_pop () or array_shift () function to remove elements from the array header or tail sequentially.
3. array key-value interchange
If you want to create an array whose key is the value of the old array and whose value is the key of the old array, simply call the key-value pair, you can use the array_flip () function to complete the operation.
The code is as follows:
$ Capitals = array (
'Babama' => 'mongomery ',
'Apache' => 'juneau ',
'Arizona '=> 'Phoenix'
);
$ States = array_flip ($ capitals );
// $ States = array (
// 'Mongomery' => string 'abama ',
// 'Juneau '=> string 'Alaska ',
// 'Phoenix '=> string 'Arizona'
//);

4. Merge arrays
If you want to combine two or more numbers into a new array, the array_merge () function can help ^_^
The code is as follows:
$ StateCapitals = array (
'Babama' => 'mongomery ',
'Apache' => 'juneau ',
'Arizona '=> 'Phoenix'
);
$ CountryCapitals = array (
'Australia '=> 'canonical ',
'Austria' => 'Vienna ',
'Algera' => 'algiers'
);
$ Capitals = array_merge ($ stateCapitals, $ countryCapitals );

5. Modify the value in array
For example, if you want to change all the values in the array to lowercase and then uppercase letters, it is a good method to recursively call each array member using the callback function. In php, this function is php_map ()
The code is as follows:
Function capitalize ($ element)
{
$ Element = strtolower ($ element );
Return ucwords ($ element );
}
$ Capitals = array (
'Babama' => 'mongomery ',
'Apache' => 'juneau ',
'Arizona '=> 'Phoenix'
);
$ Capitals = array_map ("capitalize", $ capitals );

6. Sort the array by the array key
The code is as follows:
$ Capitals = array (
'Arizona '=> 'Phoenix ',
'Apache' => 'juneau ',
'Babama' => 'mongomery'
);
Ksort ($ capitals );

7. Randomize the order of array elements
The shuffle () function is opposite to the preceding ksort () function, which can disrupt the existing order of the array to achieve randomization.
The code is as follows:
$ Capitals = array (
'Arizona '=> 'Phoenix ',
'Apache' => 'juneau ',
'Babama' => 'mongomery'
);
Shuffle ($ capitals );

8. Check whether the key or value exists.
Use the in_array () function to check whether a value exists.
The code is as follows:
$ Capitals = array (
'Arizona '=> 'Phoenix ',
'Apache' => 'juneau ',
'Babama' => 'mongomery'
);
If (in_array ("Juneau", $ capitals ))
{
Echo "Exists! ";
} Else {
Echo "Does not exist! ";
}

Find whether the key exists using the array_key_exists () function
The code is as follows:
$ Capitals = array (
'Arizona '=> 'Phoenix ',
'Apache' => 'juneau ',
'Babama' => 'mongomery'
);
If (array_key_exists ("Alaska", $ capitals ))
{
Echo "Key exists! ";
} Else {
Echo "Key does not exist! ";
}

9. Search for arrays
This is a commonplace. Basically, the array_search () function is used.
The code is as follows:
$ Capitals = array (
'Arizona '=> 'Phoenix ',
'Apache' => 'juneau ',
'Babama' => 'mongomery'
);
$ State = array_search ('juneau ', $ capitals );
// $ State = 'Alaska'

10. Use the php Standard function library
I will introduce this multi-Operation array function in one breath. If you still feel uncomfortable, you can continue to view the content in Standard PHP Library ^_^.
The code is as follows:
$ Capitals = array (
'Arizona '=> 'Phoenix ',
'Apache' => 'juneau ',
'Babama' => 'mongomery'
);
$ ArrayObject = new ArrayObject ($ capitals );
Foreach ($ arrayObject as $ state => $ capital)
{
Printf ("The capital of % s is % s <br/>", $ state, $ capital );
}
// The capital of Arizona is Phoenix
// The capital of Alaska is Juneau
// The capital of Alabama is Montgomery

 

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