Summary of php array operation methods

1. Basic functions of array operations
Key names and values ​​of arrays
array_values($arr); Get the value of the array
array_keys($arr); Get the key name of the array
array_flip( $arr); The values ​​and key names in the array are interchanged (if there are duplicates, the previous one will be overwritten by the later one)
in_array("apple",$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($arr); Return the current unit in the array
pos($arr); Return the current unit in the array Current unit
key($arr);Returns the key name of the current unit in the array
prev($arr);Rewinds the internal pointer in the array by one digit
next($arr);Returns the key name of the current unit in the array Move the internal pointer forward one bit
end($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); will return a constructed array of key names/values ​​of the current element of the array, and move the array pointer forward one bit
list($key,$value)=each($arr); get the current array element Key names and values ​​of elements

Conversion between arrays and variables
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. Value as variable value
Note: (The second parameter is very important, you can refer to the manual for use) Usage echo $a;
compact(var1,var2,var3);Create an array with the given variable name

2. Segmentation and filling of arrays
Segmentation of arrays
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 Array
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($arr,"apple","pear");Push one or more elements into the array At the end of the stack (push), return the number of elements pushed into the stack
array_pop($arr); pop the last element of the array stack(pop)

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

5. Callback function
array_walk($arr,'function',' words'); Use user function to process each member of the array (the third parameter is passed to the callback function function)
array_mpa("function",$arr1,$arr2); can process multiple arrays (when When using two or more arrays, their lengths should be the same)
array_filter($arr,"function"); Use the callback function to filter each element in the array. If 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 remain unchanged
array_reduce($arr,"function","*");converted into a single-valued function (* is the first value of the array)

6. Sorting of Arrays
Sort the array by element value
sort($arr); Sort from small to large (the second parameter is how to sort) Arrays that ignore key names Sorting
rsort($arr); Sort from large to small (the second parameter is the sorting method). Array sorting ignoring key names
usort($arr,"function");Use user-defined The defined comparison function sorts the values ​​in the array (there are two parameters in the function, 0 means equal, a positive number means the first is greater than the second, a negative number means the first is less than the second) Array sorting ignoring key names
asort($arr); Sort from small to large (the second parameter is how to sort) Array sorting with key names preserved
arsort($arr); Sort from large to small ( The second parameter is how to sort) Array sorting that preserves key names
uasort($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, a negative number means the first one is less than the second one) Array sorting that retains the key name

Sort the array by key name
ksort($ arr); Sort by key names in positive order
krsort($arr); Sort by key names in reverse order
uksort($arr,"function");Use user-defined comparison function to perform key names in the array Sorting (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 calculation
Sum of array elements
array_sum($arr);Sum 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 strings in the array Key names, 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 the 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 subsequent

array
array_diff($arr1,$arr2); returns the difference Set result array
array_diff_assoc($arr1,$arr2,$arr3); Returns the difference set result array, and the key names are also compared

Intersection of arrays
array_intersect($arr1,$arr2); Return the intersection result array
array_intersect_assoc($arr1,$arr2); Return the intersection result array, and the key names are also compared

8. Other array functions
range(0 ,12);Create an array containing cells in the specified range
array_unique($arr);Remove duplicate values ​​​​in the array, and the original key names will be retained in the new array
array_reverse($arr,TRUE); Returns an array with the cells in the reverse order of the original array. If the second parameter is TRUE, the original key names are retained.
//srand((float)microtime()*10000000); Random seed trigger
array_rand($ arr,2); Randomly take out one or more elements from the array
shuffle($arr);Shuffle the order of the array
This type of function allows multiple methods to operate and interact with the array. 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 — Split an array into multiple
array_combine — Create an array, use 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 of the array with index checking
array_diff_key — Use the key name Compare and calculate the difference of an array
array_diff_uassoc — Compute the difference of an array using a user-supplied callback function to do an index check
array_diff_ukey — Compute the difference of an array using a callback function to compare key names
array_diff — Compute an array Difference set
array_fill_keys — Fill an array with values, specifying keys
array_fill — Fill an array with given values ​​
array_filter — Use a callback function to filter cells in an array
array_flip — Swap elements in an array Keys and values ​​
array_intersect_assoc — Computes the intersection of arrays with index checking
array_intersect_key — Computes the intersection of arrays using key name comparison
array_intersect_uassoc — Computes the intersection of arrays with index checking, using a callback function Compare indices
array_intersect_ukey — Compute the intersection of arrays using callback functions to compare keys
array_intersect — Compute the intersection of arrays
array_key_exists — Check whether a given key or index exists in an array
array_keys — Returns all keys in the array
array_map — Apply a callback function to the cells of the given array
array_merge_recursive — Recursively merge one or more arrays
array_merge — Merge one or more arrays
array_multisort — Sort multiple arrays or multidimensional arrays
array_pad — Pad an array with values ​​to a specified length
array_pop — Pop (pop) the last element of an array
array_product — Calculate the value of all values ​​in an array Product
array_push — Push one or more elements to the end of the array (push)
array_rand — Randomly take one or more elements from the array
array_reduce — Use a callback function to iteratively reduce the array to A single value
array_reverse — Returns an array with the cells in reverse order
array_search — Searches the array for a given value, returning the corresponding key if successful
array_shift — Moves the cell at the beginning of the array out of the array
array_slice — Remove a segment from an array
array_splice — Remove a portion 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, Compare data using a callback function
array_udiff_uassoc — Compute the difference of an array with index checking, use a callback function to compare data and index
array_udiff — Compute the difference of an array using a callback function to compare data
array_uintersect_assoc — Calculate the intersection of arrays with index checking and use callback functions to compare data
array_uintersect_uassoc — Calculate the intersection of arrays with index checking, use a callback function to compare the data and index
array_uintersect — Calculate the intersection of arrays, use a callback function to compare the data
array_unique — Remove duplicate values ​​in the array
array_unshift — Insert one or more cells at the beginning of the array
array_values ​​— Return all values ​​in the array
array_walk_recursive — Recursively apply a user function to each member of the array
array_walk — Recursively apply the Apply the user function to each member of
array — Create a new array
arsort — Sort the array in reverse and maintain the index relationship
asort — Sort the array and maintain the index relationship
compact — Create an array , including variable names and their values ​​
count — Counts the number of cells in an array or the number of attributes in an object
current — Returns the current cell in the array
each — Returns the current key/value pair in the array And move the array pointer one step forward
end — Point the internal pointer of the array to the last element
extract — Import variables from the array into the current symbol table
in_array — Check whether a certain element exists in the array value
key — Get the key name from the associative array
krsort — Sort the array in reverse order by the key name
ksort — Sort the array by the key name
list — Assign the values ​​in the array to some variables
natcasesort — Sort an array case-insensitively using the “natural sort” algorithm
natsort — Sort an array using the “natural sort” algorithm
next — Move the internal pointer in the array forward by one bit
pos — Alias ​​for current()
prev — Rewind the internal pointer of the array by one bit
range — Create an array containing the specified range cells
reset — Set the internal pointer of the array to point to the A unit
rsort — Sort an array in reverse order
shuffle — Shuffle an array
sizeof — Alias ​​for count()
sort — Sort an array
uasort — Use a user-defined comparison Function sorts the values ​​in an array while maintaining index association
uksort — Sorts the keys in an array using a user-defined comparison function
usor — Sorts the values ​​in an array using a user-defined comparison function Sort

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