Summary of commonly used array functions in PHP

This article mainly shares with you a summary of commonly used array functions in PHP. We will share it with you in six parts. The first part is the basic functions of array operations, the second part is the segmentation and filling of the array, and the third part is...

Key name and value of the array

array_values($arr); Get the values ​​of the array
array_keys($arr); Get the key name of the array
array_flip($arr); Exchange the values ​​​​with the key names in the array (if there are duplicates The former will be overwritten by the latter)
in_array("apple",$arr); Retrieve apple in the array
array_search("apple",$arr); Retrieve apple in the array, if it exists, return the key name
array_key_exists("apple",$arr); Retrieve whether the given key name exists in the array
isset($arr[apple]): Retrieve whether the given key name exists in the array

Internal pointer of the array

current($arr); Returns the current unit in the array
pos($arr); Returns the current unit in the array
key($arr); Returns the current unit in the array The key name of the current unit
prev($arr); Move the internal pointer in the array back one bit
next($arr); Move the internal pointer in the array forward one bit
end($ arr); Point the internal pointer in the array to the last unit
reset($arr; Point the internal pointer in the array to the first unit
each($arr); Returns a key name of the current element of the array /Construct an array of values ​​and move the array pointer forward one bit
list($key,$value)=each($arr); Obtain the key name and value of the current element of the array

Arrays and variables Conversion between

extract($arr); is used to convert the elements in the array into variables and import them into the current file. The key name is used as the variable name and the value is used as the variable value
Note: (No. The two parameters are very important, you can refer to the manual for use.) Use the method echo $a;
compact(var1,var2,var3);Create an array with the given variable name

2. Segmentation of the array And fill the segment of the

array

array_slice($arr,0,3); You can take out a segment of the array, this function ignores the key name
array_splice($arr,0 ,3.array("black","maroon")); You can take out a section of the array. The difference from the previous function is that the returned sequence is deleted from the original array

Split multiple arrays

array_chunk($arr,3,TRUE); You can split an array into multiple ones. TRUE retains the key name of the original array.

Filling of the array

array_pad($arr, 5,'x'); Fill an array to the specified length

3. Array and stack

array_push($arr,"apple","pear"); Fill one or more Push the element to the end of the array stack (push) and return the number of elements pushed into the stack
array_pop($arr); Pop the last element of the array stack (pop off the stack)

4. Arrays and Queue

array_shift($arr);The first element in the array is moved out and returned as the result (the array length is reduced by 1, other elements are moved forward one position, the numeric key name is changed to zero technology, and the text key The name remains unchanged)
array_unshift($arr,"a",array(1,2));Insert one or more elements at the beginning of the array

5. Callback function

array_walk($arr,'function','words'); Use user function to process each member in the array (the third parameter is passed to the callback function function)
array_mpa("function",$arr1,$ arr2); Can handle multiple arrays (when using two or more arrays, their lengths should be the same)
array_filter($arr,"function"); Use the callback function to filter each element in the array, if If the callback function is TRUE, the current element of the array will be included in the returned result array, and the key names of the array will remain unchanged
array_reduce($arr,"function","*"); Convert to a single-valued function (* is the first value of the array)

6. Sorting of the array

Sort the array by element value

sort($arr); Sort from small to large (The second parameter is how to sort) Ignore the array sorting of key names
rsort($arr); Sort from large to small (The second parameter is how to sort) Ignore the array sorting of key names
usort($arr,"function"); Use a user-defined comparison function to sort the values ​​in the array (there are two parameters in the function, 0 means equal, a positive number means the first one is greater than the second one, Negative number means the first one is smaller than the second one) Ignore the array sorting of key names
asort($arr); Sort from small to large (the second parameter is the sorting method) Keep the array sorting of key names
arsort($arr); Sort from large to small (the second parameter is how to sort). Array sorting with key names preserved.
uasort($arr,"function"); Use user-defined The comparison function sorts the values ​​in the array (there are two parameters in the function, 0 means equal, a positive number means the first is greater than the second, a negative number means the first is less than the second) Array sorting preserving key names

Sort array by key name

ksort($arr); Sort by key name in positive order
krsort($arr); Sort by key name in reverse order
uksort($arr,"function"); Use user-defined comparison function Sort the key names in the array (there are two parameters in the function, 0 means equal, a positive number means the first is greater than the second, a negative number means the first is less than the second)

Natural sorting method sorting

natsort($arr); Natural sorting (ignore key names)
natcasesort($arr); Natural sorting (ignore case, ignore key names)

7. Array calculations

Sum of array elements

array_sum($arr); Perform sum operation on all elements inside the array

Merge of arrays

array_merge( $arr1,$arr2); Merge two or more arrays (the same string key name, the latter one overwrites the previous one, the same numeric key name, the latter one will not be overwritten, but will be appended to the end)
“+”$arr1+$arr2; For the same key name, only the last one is retained
array_merge_recursive($arr1,$arr2); Recursive merge operation, if there are the same string key names in the array, these values ​​will be merged into an array. If a value itself is an array, it will be merged into another array according to the corresponding key name. When arrays have the same array key name, the latter value will not overwrite the original value, but will be appended to the difference set of the following

array_diff($arr1,$arr2) ; Returns the difference set result array

Intersection of the arrays

array_intersect($ arr1,$arr2); Returns the intersection result array

8. Other array functions

range(0,12); Create an array containing the specified range of units

array_reverse($arr, TRUE); Returns an array in which the order of cells is reversed from the original array. If the second parameter is TRUE, the original key name is retained
//srand((float)microtime()*10000000); Random seed trigger
array_rand($arr,2); Randomly remove one or more elements from the array
shuffle($arr); Shuffle the order of the array

This type of function allows multiple methods to operate the array and interact with it. The essence of an array is to store, manage and operate a set of variables.

PHP supports one- and multi-dimensional arrays, which can be created by the user or by another function. There are specific database handling functions that generate arrays from database queries, and there are functions that return arrays.

array_change_key_case — Returns an array whose string keys are all lowercase or uppercase

array_chunk — Splits an array into multiple

array_combine — Creates an array, using an array The value of the array is used as its key name, and the value of another array is used as its value

array_count_values ​​— Count the number of occurrences of all values ​​in the array

array_diff_assoc — Calculate the difference set of the array with index check

array_diff_key — Computes the difference of an array using key name comparison

array_diff_uassoc — Computes the difference of an array using a user-supplied callback function for index checking

array_diff_ukey — Uses a callback function to Compare key names to calculate the difference of an array

array_diff — Calculate the difference of an array

array_fill_keys — Fill an array with values, specifying keys

array_fill — Use the given value Populate an array

array_filter — Filter elements in an array using a callback function

array_flip — Swap the keys and values ​​in an array

array_intersect_assoc — Compute the intersection of arrays with index checking

array_intersect_key — Computes the intersection of arrays using key comparisons

array_intersect_uassoc — Computes the intersection of arrays with index checking, using callback functions to compare indices

array_intersect_ukey — Uses callback functions to compare keys Calculate the intersection of arrays

array_intersect — Calculate the intersection of arrays

array_key_exists — Check whether the given key name or index exists in the array

array_keys — Return all the keys in the array Key

array_map — Apply the callback function to the cells of the given array

array_merge_recursive — Recursively merge one or more arrays

array_merge — Merge one or more Array

array_multisort — Sort multiple arrays or multidimensional arrays

array_pad — Pad the array to the specified length with values ​​

array_pop — Pop the last element of the array out stack)

array_product — Calculate the product of all values ​​in an array

array_push — Push one or more elements to the end of the array (push)

array_rand — From an array Randomly take one or more cells from

array_reduce — Use a callback function to iteratively reduce the array to a single value

array_reverse — Return an array with the cells in the reverse order

array_search — Search for the given value in the array, and if successful, return the corresponding key name

array_shift — Move the unit at the beginning of the array out of the array

array_slice — Remove a segment from the array

array_splice — Remove part of an array and replace it with another value

array_sum — Calculate the sum of all values ​​in an array

array_udiff_assoc — Calculate the difference of an array with index checking, use a callback function to compare the data

array_udiff_uassoc — Calculate the difference of an array with an index check, use a callback function to compare the data and index

array_udiff — Calculate the difference of arrays by comparing data with a callback function

array_uintersect_assoc — Calculate the intersection of arrays with index checking, compare data with a callback function

array_uintersect_uassoc — Calculate the intersection of arrays with index checking, use Callback function compares data and index

array_uintersect — Calculates the intersection of arrays, compares data with callback function

array_unique — Removes duplicate values ​​in the array

array_unshift — At the beginning of the array Insert one or more cells

array_values ​​— Returns all values ​​in an array

array_walk_recursive — Recursively applies a user function to each member of an array

array_walk — Recursively applies a user function to each member of an array Apply user functions to each member in

array — Create a new array

arsort — Sort the array in reverse order and maintain the index relationship

asort — Sort the array and maintain Index relationship

compact — Create an array, including variable names and their values

count — Count the number of cells in the array or the number of attributes in the object

current — Return The current element in the array

each — Returns the current key/value pair in the array and moves the array pointer one step forward

end — Points the internal pointer of the array to the last element

extract — Import variables from an array into the current symbol table

in_array — Check whether a value exists in the array

key — Get the key name from an associative array

krsort — Sort the array in reverse order by key

ksort — Sort the array by key

list — Assign the values ​​in the array to some variables

natcasesort — Sort the array case-insensitively using the “natural sort” algorithm

natsort — Sort the array using the “natural sort” algorithm

range — Create an array containing cells in the specified range

reset — Point the internal pointer of the array to the first element

rsort — Reverse sort the array

shuffle — Shuffle the array

sort — Sort an array

uasort — Use a user-defined comparison function to sort the values ​​in an array and maintain index association

uksort — Use a user-defined comparison function to sort the keys in an array Sorting

usort — Use user-defined comparison functions to sort values ​​in an array

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