Some commonly used PHP array functions_PHP tutorial-PHP Tutorial-php.cn

Proficiency in using arrays can sometimes solve many problems. If you are familiar with the relevant functions, you will get twice the result with half the effort. Take a look at the following functions related to arrays. Are you familiar with them?

1. Basic functions of array operations

Key name and value of array

array_values($arr); Get the value of the array
array_keys($arr); Get the key name of the array
array_flip($arr); The values and key names in the array are interchanged (if there are duplicates, the previous ones will be overwritten by the later ones)
in_array("apple",$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 to array

current($arr); returns the current unit in the array
pos($arr); returns the current unit in the array
key($arr); returns the key name of the current unit in the array
prev($arr); Reverse the internal pointer in the array by one position
next($arr); Move the internal pointer in the array forward one position
end($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 array

array_slice($arr,0,3); can remove a segment from the array. This function ignores the key name
array_splice($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 array

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

3. Arrays and stacks

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

4. Arrays and Queues

array_shift($arr); The first element in the array is moved out and returned as the result (the length of the array is reduced by 1, other elements are moved forward one position, the numeric key name is changed to zero technology, and the text key name remains unchanged)
array_unshift($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 names of the array will remain unchanged. Change
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($arr); Sort from small to large (the second parameter is how to sort) array sorting ignoring key names
rsort($arr); Sort from large to small (the second parameter is how to sort) Array sorting ignoring key names
usort($arr,"function"); Use a user-defined comparison function to sort the values in the array (there are two parameters in the function, 0 means equal, a positive number means the first one is greater than the second one, Negative numbers mean the first is smaller than the second) Array sorting ignoring key names
asort($arr); Sort from small to large (the second parameter is the sorting method) and preserve the array sorting of key names
arsort($arr); sort from large to small (the second parameter is how to sort) array sorting with key names preserved
uasort($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, Negative numbers indicate that the first is smaller than the second) array sorting that preserves 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 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. Array calculation

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 appended to the back) "+"$arr1+$arr2; for the same key name, only keep the last one
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 back

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 the intersection result array, and the key names are also compared

8. Other array functions

Sum of array elements

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 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