A complete list of built-in functions for php arrays

1.array_change_key_case($arr,CASE_UPPER/CASE_LOWER) Convert the key value of $arr to uppercase or lowercase

2.array_combine($arr1, $arr2) The value of $arr1 is used as the key, and $arr2 is generated as the value and a new array is returned

3.array_key_exists('key', $arr) Whether the key exists in $arr, Returns true if it exists, returns false if it does not exist

4.array_keys($arr) returns all key values ​​​​in $arr in the form of an array

5.array_values($arr) in the form of an array Return the values ​​of all values ​​in $arr

6.count($arr, $mode=COUNT_NORMAL)Calculate the number of arrays

7.array_count_values($arr ) Calculate the number of occurrences of the value in the array to form a new array. The key is the value of the original array and the value is the number of occurrences.

8.sort($arr, $mode) Important sorting array function

$mode is:

①SORT_REGULAR, 0, default item, regular sorting, sorting according to ASCII, does not change the type.

②SORT_NEMERIC, 1, treat each item as a number

③SORT_STRING, 2, treat each item as a string

④SORT_LOCALE_STRING, 3, treat each item Items are processed as strings, based on the current locale (can be changed by setlocale())

⑤SORT_NATURAL, 4, each item is processed as a string, using a natural sort similar to natsort()

⑥SORT_FLAG_CASE, 5, you can combine (bitwise OR) SORT_STRING or SORT_NATURAL to sort strings, case-insensitive

9.ksort($arr,$sort_flags) sorts the array in ascending order by key name Arrange, the corresponding krsort() sorts the array in descending order by key name

10.asort($arr,$sort_flags) sorts the array in ascending order of values, asort() sorts the array in descending order of values

11.shuffle() randomly shuffles the elements in the array and generates new keys

12.array_flip($arr) exchanges the keys and values ​​of the array, generates a new array and returns

13.array_unique($arr) deletes duplicate values ​​from the array, generates a new array and returns

14.array_pop($arr) deletes the last element of the array, Returns the value of the deleted element. The corresponding array_push(array &$array, $var, $_ =null) inserts the value of $var at the end of the array $array. Multiple values ​​can also be inserted, and the new number of $array is returned.

15.array_shift($arr) deletes the first element of the array and returns the value of the deleted element, corresponding array_unshift(array &$array,$var,$_= null )Insert the value of $var at the beginning of the array $array. You can also insert multiple values, and return the new number of $array.

16.array_sum($arr) calculates the sum of all values ​​in the array and returns , ensure that the values ​​in the array are all numbers

17.compact($varname, $_=null) is an important function that connects variables and returns an array. The key is the variable name, and the value corresponds to the value of $varname.

18.extract($arr,$extract_type =null,$pre_fix=null), conveniently create each element in the array into a corresponding variable, the variable name is key (if $pre_fix is ​​set, it will Add prefix), value corresponds to the value of the variable.

19.in_array($needle, array $haystack, $strict = null) finds whether there is an element equal to the $needle value in $haystack (= =) If strict is true, strict search mode is enabled and types will be compared.

20.array_rand(array $input,$num_req=null) Randomly extract $num_req elements from the $input array and return the array It consists of key (not including value) or a key.

21.array_merge($array1,$array2) merges two arrays. The rule index subscript will automatically redistribute the subscript, and the associated subscript will Overwrite the previous value with the later value.

22.unset($arr['key']) deletes the specified element in the array

23.serialize($arr) serializes the array and returns String, unserialize($str) deserializes the string and converts it into an array, in order to save the array into the file database.

24.array_slice($array, $offset,$length,$preserve_keys=null ) intercept $length elements starting from the $offset position of array and return the intercepted array.

25.array_splice(array &$input, $offset,$length=null,$replacement = null) will input array $length elements are intercepted starting from the $offset position, $replacement is inserted at this position, $input is changed, and the replaced array is returned.
Supplement: sort method sorting and shuffle() will generate new keys, ksort() and asort() does not work. Items 14 and 15 use arrays to implement queue and stack data structures commonly used.

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