Detailed explanation of php array processing function

This article mainly shares with you the detailed explanation of PHP array processing functions, hoping to help everyone.

1. Since the array is composed of key values ​​and element values, there are many functions that operate on key values ​​and elements.

1.array_values($contact):

Do not retain the key name, arrange the array according to the index

2.array_keys($contact,'optional parameter', 'Optional parameter true/false'):

If the optional parameter is set, the key name will be returned according to the optional parameter. If it is not set, the key name of the array will be returned directly. False means that it does not rely on the default parameter type

3.in_array('value','$contact','optional parameter true/false'):

Check whether there is a value in the array, the true type must be exactly the same, search value If it is a string, after setting true, the size will be distinguished

4.array_search('element value',$lamp,'optional parameter true/false')

true strict variable subscript

array_key_exists('element value', $contact):

5.array_flip($contact):

Exchange the key name and element value of the array, if a value Appears multiple times, the last key name is its value

6.array_reverse($contact,'optional parameter true/false'):

Reverse the order of the array, true keeps the key name Unchanged

II. Functions related to the number of array elements

1.count($contact,'optional parameter 0/1'):

Counts the number of elements in the array, the optional parameter indicates whether it is recursive Detect multi-dimensional arrays, 0 means no detection, 1 means detection

2.array_count_values($contact):

Count the number of occurrences of array elements, output the array, the key name is the element value, Harajuku position Number of occurrences

3.array_unique($contact):

Delete duplicate element values ​​in the array, duplicate elements, and key names retain the key name of the first element

three. Functions that use callback functions to process arrays

1.array_filter($contact,'optional "called function"'):

The callback function returns true, the current array value is retained, and the final output

2.array_walk($contact,'callback function','optional parameter'):

The callback function passes in two parameters, the first parameter is the array element value, the second parameter The parameter is the key name

3.array_map('callback function', $contact,' optional parameter array $contact1'):

When only one array is passed in, follow the callback function Call output, the same applies to multiple arrays

When the callback function is empty, two arrays with the same length are output. The parallel callback means that after calling the first element of the first array, it calls the second element of the second array. two elements, and then call them in sequence. If the array lengths are different, the short array will be supplemented with empty cells

four. Array sorting function

1.sort() and rsort():

The internal elements of the array are sorted from small to large

The internal elements of the array are sorted from large to small

Discard the original index of the array element

2.ksort() and Krsort()

Sort the array according to the key name

According to Sort the key names from small to large

Sort the key names from large to small

3.asort() and arsort()

Sort according to the element value, retain the key name

4. Sort the array according to the natural sorting method

natsort() and natcasesort()

Sort the array according to numbers from 1 to 9 and letters from a to z. The former Ignore the key name, the latter retains the key name, and the former is case-sensitive, the latter is not case-sensitive

5.usort():

User-defined

6 .Sorting of multi-dimensional arrays:

array_multisort(), continuously sorting according to the value of the array

5. Split, merge, decompose, combine arrays

1.array_slice($contact,'Get the initial value of the element','Optional parameter: Get the length of the element','Optional parameter: true/false'):

Get the initial value of the element If the value is positive, it will be taken from front to back. If the value is negative, it will be taken from front to back. If the last element is -1, it will be taken from the negative value backward.

true will retain the key name,

2.array_splice($contact,'Delete the initial value of the element' , 'length of deleted element', 'optional parameter: replacement array'):

If the initial value is a positive number, deletion will start from this value. Negative numbers are the same as slice(). If the replacement array is set, then Insert the replacement array at the deleted location.

3.array_combine($contact1,$contact2):

The two arrays must have the same number of elements. The first array element is the key value, and the second array element is the element value.

4.array_merge($contact1,$contact2):

The first parameter is a required parameter, only one will be output in the form of an index array, multiple arrays are merged, and the key name Repeat, the latter overwrites the previous

5.array_intersect($contact1,$contact2):

Intersection of the arrays, the key name remains unchanged, only the array values ​​are compared, and the first array is output Common to both of them

6.array_diff($contact1,$contact2,$contact3):

The difference set of arrays, the first array and the second parameter are required Parameters, the third parameter is even optional in the future, and the output value is in one array but not in other arrays.

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