PHP array related functions_PHP tutorial

ange($low, $high),range($low, $high, $step);//Create an array of sequential values ​​such as: range(1,4) is (1,2,3,4) and range( 'a','z')

each($array) returns the current element of the array in order, and sets the next element to the current element;

reset($array) resets the array The current element is reset to the beginning of the array

list() can be used to decompose an array into a series of values, such as list($a,$b)=each($array)

shuffle($array), array_rand($arg, $num_req); Randomly sort the array

array_reverse($input), array_reverse($input, $preserve_keys) Return the reverse sorting of the original array

sort($array); Sort the array



PHP array is an important concept. It contains a large number of functions to facilitate people's development... Now classify its arrays , to facilitate query and application.
Let’s talk about the definition of PHP array first... PHP array contains two items, key and value. The corresponding value can be obtained through key, where key can be numerical and associated, such as $ array[0],$array[one]…
Create array
The array declaration in PHP is slightly different from that in other languages, but it can still be declared as one-dimensional, two-dimensional, three-dimensional and multi-dimensional. , such as
$array[0] = 1,$array = array(1,2,3); a one-dimensional array, including only three values, is a numeric array, and can be represented by $array[0] when referencing 1. The index can be omitted when creating a numerical array.

Copy code The code is as follows:

$array = array(
1 => “one”,
2 => “two”,
3 => “three”,
4 => array(
“one” => 1,
“two” => 2,
“three” => 3
)
);

A two-dimensional array, which is also an associative array, can be referenced by $array[4]["one"] to represent 1.
The same goes for three-dimensional and above...
If you want to create arrays in batches, you can Through the following function:
array range (mixed low, mixed high [, number step])
For example, $array = range(1,6); represents array(1,2,3,4,5,6 );
$array = range(a,f); represents array(a,b,c,d,e,f);

Output array
The functions that output arrays in PHP have comparisons Many, commonly used ones include
bool print_r ( mixed expression [, bool return] )
void var_dump ( mixed expression [, mixed expression [, ...]] )
and echo, print, printf Both can output a single array.

Test array
Sometimes we need to determine whether a variable is an array, you can use:
bool is_array (mixed var)

Add or delete an array The element
array is not immutable after it is declared. In-depth operations may be performed by adding or deleting the array:
int array_push (array &array, mixed var [, mixed ...] ) Will one or more units Push the end of the array, the length of the array increases according to the number of variables pushed onto the stack, such as array_push($array,$var)
mixed array_pop (array &array) pops the last element of the array (pops the stack), and ends After resetting the array pointer
mixed array_shift ( array &array ) returns the first element of the array.
int array_unshift ( array &array, mixed var [, mixed ...] ) inserts one or more elements at the beginning of the array units
array array_pad (array input, int pad_size, mixed pad_value) fills the array to the specified length with values, such as array_pad($array,3,$var);

positioning array elements
bool in_array (mixed needle, array haystack [, bool strict]) Check whether a certain value exists in the array
array array_keys (array input [, mixed search_value [, bool strict]]) Return all key names in the array, Reorganize into a new array
bool array_key_exists ( mixed key, array search ) Check if the given key exists in the array.
array array_values ​​( array input ) Return all values ​​in the array
mixed array_search ( mixed needle, array haystack [, bool strict] ) Search for the given value in the array, and return the key if successful.

Traverse the array
PHP provides many functions for obtaining key and value
mixed key (array &array) Get the key name from the associative array
mixed reset (array &array) Reset the array pointer
array each (array &array) Return the key/value pair in the array and move the array forward one step
mixed current (array &array) returns the current unit in the array
mixed end (array &array) moves the pointer in the array to the last bit
mixed next (array &array) moves the pointer in the array to Next bit
mixed prev (array &array) Move the pointer in the array to the previous bit
array array_reverse (array array [, bool preserve_keys]) Return an array with the cells in reverse order
array array_flip (array trans ) Reverse the key-value roles in the array
In addition to the above functions, you can also use loops to traverse the elements in the array, such as
foreach (array_expr as $value)
{ statement }
foreach (array_expr as $key=>$value)
{ statement }
Extract each key/value pair until all items are obtained or some internal conditions are met
void list ( mixed varname, mixed ... ) Assign the values ​​in the array to some variables

Determine the size and uniqueness of the array
int count (mixed var [, int mode]) counts the number of attributes in the unit array or object in the array, the function of the same name of sizeof
array array_count_values ​​(array input) counts in the array The number of occurrences of all values
array array_unique (array array) Remove duplicate values ​​in the array

Array sorting
I heard that this is the core problem of calculators... Haha... This is also true...
bool sort (array &array [, int sort_flags]) sorts an array
bool natsort (array &array) sorts an array using natural sorting
bool natcasesort (array &array) sorts an array using natural sorting , case-insensitive
bool rsort (array &array [, int sort_flags]) Sort the array in reverse order
bool asort (array &array [, int sort_flags]) Sort the array and maintain the index relationship
bool array_multisort ( array ar1 [, mixed arg [, mixed ... [, array ...]]] ) Sort multiple arrays or multidimensional arrays
bool arsort ( array &array [, int sort_flags] ) Sort arrays Sort in reverse order and maintain index relationship
bool ksort (array &array [, int sort_flags]) Sort the array by key name
bool krsort (array &array [, int sort_flags]) Sort the array in reverse order by key name

Combine, split, join and decompose arrays
array array_combine (array keys, array values) creates an array with the values ​​of one array as its keys and the values ​​of another array as its values
array array_merge ( array array1 [, array array2 [, array ...]] ) Merge one or more arrays
array array_merge_recursive ( array array1 [, array ...]) Recursively merge all one or more arrays
array array_slice ( array array, int offset [, int length [, bool preserve_keys]] ) Remove a segment from the array and create a new array. If offset is a positive number, splitting starts from the offset position from the array switch. If it is a negative number, then Splitting starts from the offset position from the end of the array, which ends at the count(input_array)-|length| position of the array switch
array array_splice (array &input, int offset [, int length [, array replacement]] ) Remove some values ​​in the array and replace them with other values. The offset setting is the same as above
array array_intersect (array array1, array array2 [, array...]) Calculates the intersection of the arrays, that is, if it appears in the first array The value appears in the next several arrays, then take out the value
array array_intersect_assoc (array array1, array array2 [, array...]) Check the intersection in the array with index
array array_intersect_key ( array array1, array array2 [, array ...] ) Use the key name to compare the intersection in the array
array array_diff ( array array1, array array2 [, array ...] ) Calculate the difference of the array, that is, with Different values ​​in the first array
array array_diff_assoc ( array array1, array array2 [, array ...] ) Checking the difference in the array with index
array array_diff_key ( array array1, array array2 [, array . ..] ) Use key names to compare differences in arrays

Other useful array functions
There are many array functions not listed... Here are a few more useful and common ones, and others Just refer to the manual... The manual is very clear:
mixed array_rand (array input [, int num_req]) randomly takes out one or more keys from the array, num specifies the number
bool shuffle (array &array) shuffles the array
number array_sum (array array) Calculate the sum of all values ​​in the array, associative arrays are ignored
array array_chunk (array input, int size [, bool preserve_keys]) Split an array into several

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