A complete collection of php array operation methods

1. Basic functions Key name and value of array array_values($arr); Get the values ​​of the array array_keys($arr); Get the key name of the array array_flip($arr); The values ​​in the array are interchanged with the key names (if there are duplicates, the previous ones will be overwritten by the later ones) in_array("apple",$arr);Retrieve apple in array array_search("apple",$arr); Retrieve apple in the array, return the key name if it exists array_key_exists("apple",$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 array current($arr); returns the current cell in the array pos($arr); returns the current unit in the array key($arr); returns the key name of the current unit in the array prev($arr); rewind the internal pointer in the array by one bit next($arr); moves the internal pointer in the array forward one position end($arr); points the internal pointer in the array to the last element reset($arr; points the internal pointer in the array to the first element each($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 key name and value of the current element of the array

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 and the value is used as the 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($arr,0,3); you can take out a segment from the array, this function ignores the key name array_splice($arr,0,3,array("black","maroon")); 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); can split an array into multiple ones, TRUE means retaining the key names of the original array

Padding of arrays array_pad($arr,5,'x'); Pad an array to the specified length

3. Arrays and stacks array_push($arr,"apple","pear"); Push one or more elements into the end of the array stack (push) and return the number of elements pushed into the stack array_pop($arr); Pop the last element of the array stack

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

5. Callback function array_walk($arr,'function','words');Use user function to process each member in the array (the third parameter is passed to the callback function function) array_mpa("function",$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 the callback function is TRUE, the current element of the array will be included in the returned result array, and the key name of the array remains unchanged. array_reduce($arr,"function","*");Convert to a single-valued function (* is the first value of the array)

6. Sorting of arrays Sort array by element value sort($arr); Sort from small to large (the second parameter is the sorting method) and ignore the array sorting of key names. rsort($arr); Sort from large to small (the second parameter is the sorting method), ignoring the array sorting of key names usort($arr,"function"); uses a user-defined comparison function to sort the values ​​in the array (there are two parameters in the function, 0 means equal, a positive number means the first one is greater than the second one, and a negative number means the second one is greater than the second one. one is smaller than the second) array sorting ignoring key names asort($arr); Sort from small to large (the second parameter is the sorting method) and preserve the array sorting of key names. arsort($arr); Sort from large to small (the second parameter is the sorting method) and preserve the array sorting of key names. uasort($arr,"function"); uses 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, and a negative number means the second one is greater than the second one. one smaller 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"); uses a user-defined comparison function to sort the key names 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 smaller than the second one)

Natural sorting method natsort($arr); natural sorting (ignoring key names) natcasesort($arr);Natural sorting (ignore case, ignore key name)

7. Calculation of arrays Sum of array elements array_sum($arr); performs 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 latter 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 one 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 end

Difference of arrays array_diff($arr1,$arr2); returns the difference result array array_diff_assoc($arr1,$arr2,$arr3); returns an array of difference set results, and the key names are also compared

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

8. Other array functions range(0,12);Creates 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 order of cells reversed to the original array. If the second parameter is TRUE, the original key names are retained. //srand((float)microtime()*10000000); Random seed trigger array_rand($arr,2); Randomly remove one or more elements from the array shuffle($arr); shuffle the order of the array Functions of this class allow many ways to manipulate and interact with arrays. 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 with values ​​from one array as keys and values ​​from another array as values array_count_values ​​— Count the number of occurrences of all values ​​in an array array_diff_assoc — Compute the difference of an array with index checking array_diff_key — Compute the difference of an array using key comparison array_diff_uassoc — Compute the difference of an array using a user-supplied callback function with index checking array_diff_ukey — Calculate the difference of an array using a callback function to compare keys array_diff — Compute the difference of an array array_fill_keys — Fill an array with values, specifying keys array_fill — Fill an array with given values array_filter — Filter elements in an array using a callback function array_flip — swap keys and values ​​in an array array_intersect_assoc — Compute the intersection of arrays with index checking array_intersect_key — Compute the intersection of arrays using key comparison array_intersect_uassoc — Computes the intersection of arrays with index checking, using a callback function to compare the 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 if a given key or index exists in an array array_keys — Returns all keys in an array array_map — apply a callback function to the elements of the given array array_merge_recursive — Merge one or more arrays recursively array_merge — merge one or more arrays array_multisort — Sort multiple arrays or multidimensional arrays array_pad — Pad an array to a specified length with values array_pop — Pop the last element of the array (pop it off the stack) array_product — Calculate the product of all values ​​in an array array_push — Push one or more elements to the end of an array (push) array_rand — Randomly remove one or more elements from an array array_reduce — Iteratively reduce an array to a single value using a callback function array_reverse — Returns an array with the elements in reverse order array_search — Search for a given value in an array, returning the corresponding key if successful array_shift — Shift elements at the beginning of an array out of the array array_slice — Remove a segment from an array array_splice — Remove part of an array and replace it with another value array_sum — Calculates the sum of all values ​​in an array array_udiff_assoc — Computes the difference of an array with index checking and compares the data using a callback function array_udiff_uassoc — Computes the difference of an array with index checking, using a callback function to compare the data and index array_udiff — Calculate the difference of an array by comparing data using a callback function array_uintersect_assoc — Compute the intersection of arrays with index checking and compare data using callback functions array_uintersect_uassoc — Computes the intersection of arrays with index checking, using a callback function to compare data and indexes array_uintersect — Calculate the intersection of arrays, using callback functions to compare data array_unique — Remove duplicate values ​​from an array array_unshift — Insert one or more cells at the beginning of an array array_values ​​— Returns all values ​​in an array array_walk_recursive — Recursively apply a user function to each member of an array array_walk — Apply a user function to each member of an array array — create a new array arsort — Sort an array in reverse order while maintaining index relationships asort — Sort an array while maintaining index relationships compact — Create an array including variable names and their values count — Count the number of elements in an array or the number of attributes in an object current — Returns the current element in the array each — Returns the current key/value pair in the array and moves the array pointer forward one step end — Set 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 an array key — get the key name from an associative array krsort — sort an array in reverse order by key ksort — Sort an array by key list — assign values ​​from an array to variables natcasesort — Case-insensitive sorting of an array using the "natural sort" algorithm natsort — Sort an array using the "natural sorting" algorithm next — Move the internal pointer in the array forward one position pos — alias for current() prev — rewind the array’s internal pointer one bit range — Create an array containing cells in a specified range reset — Set the array's internal pointer to the first element rsort — Sort an array in reverse order shuffle — shuffle an array sizeof — Alias ​​for count() sort — sort an array uasort — Sort values ​​in an array using a user-defined comparison function and maintain index association uksort — Sort keys in an array using a user-defined comparison function usort — Sort values ​​in an array using a user-defined comparison function

Use arrays In the previous chapters, the variables we introduced were all scalar variables, which can only store a single piece of data. An array is a variable that can store a set or series of values. An array can have many elements. Each element has a value, such as text, a number, or another array. An array that contains other arrays is called a multidimensional array.