PHP Array function classification, phparray function_PHP tutorial

PHP Array function classification, phparray function

1. Basic functions of array operations
1. Array key names and values
array_values($arr); Get the value of the array
array_keys($arr); Get the key name of the array
array_flip($arr); Swap the values ​​and keys in the array ( If there are duplicates The former will be overwritten by the latter)
in_array("apple",$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($arr[apple]): Retrieve whether the given key name exists in the array
2. The internal pointer of the array
current($arr); Returns the current unit in the array
pos($arr); Returns the current unit in the array
key($arr); Return The key name of the current unit in the array
Prev ($ arr); pour the internal pointer in the array back to a
Next ($ ARR); move the internal pointer in the array forward ($arr); Point the internal pointer in the array to the last element
reset($arr; Point the internal pointer in the array to the first element
each($arr); Will return one of the current elements of the array Construct an array of key names/values ​​and move the array pointer forward one bit
list($key,$value)=each($arr); Get the key name and value of the current element of the array

3 , Conversion between arrays and variables extract($arr); 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
compact(var1,var2,var3);Create an array with the given variable name

2. Array segmentation and filling
1. Array segmentation 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")); 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

2. Split multiple arraysarray_chunk($arr,3,TRUE); An array can be split into multiple ones. TRUE means the key name of the original array is retained

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

3. Array and stackarray_push($arr,"apple","pear"); Push one or more elements into the end of the array stack (push) , returns the number of elements pushed onto the stack
array_pop($arr); Pops (pops) 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 functionarray_walk($arr,'function','words '); Use user function to process each member of the array (the third parameter is passed to the callback function function)
array_map("function",$arr1,$arr2); Can process multiple arrays (when using When there are two or more arrays, their lengths should be the same)
array_filter($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, the key name of the array remains unchanged
array_reduce($arr,"function","*"); Converted into a single-valued function (* is the first value of the array)

6. Sorting of arrays
1. Sort the array by element valuesort($arr); Sort from small to large (the second parameter is How to sort) Ignore the array sorting of key names
rsort($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, a negative number means the first one is less than Second) Array sorting ignoring key names
asort($arr); Sort from small to large (the second parameter is how to sort) Array sorting that preserves key names
arsort($arr); Sort from large to small (the second The parameter is how to sort) Array sorting that retains key names
uasort($arr,"function"); Use a user-defined comparison function to sort the values ​​in the array (there are two parameters in the function, 0 means Equality, a positive number means the first one is greater than the second one, a negative number means the first one is less than the second one) Array sorting with key names preserved
2. Sort the array by key name
ksort ($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 to compare the keys in the array Sort by name (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)
3. Sorting by natural sorting
natsort($arr); Natural sorting (ignore key names)
natcasesort($arr); Natural sorting (ignore case, ignore key names)
7. Array calculations
1. Sum of array elements
array_sum($arr); Perform sum operation on all elements inside the array
2. Merge of arrays
array_merge($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 $arr2; For the same key name, only the last one is retained
array_merge_recursive($arr1,$arr2); Recursive merge operation, if there are the same string key names in the array, these values ​​will be Merge into an array. If a value itself is an array, it will be merged into another array according to the corresponding key name. When the arrays have the same array key name, the latter value will not overwrite the original value, but will be appended to the following
3. Array difference
array_diff($arr1,$ arr2); Returns an array of difference set results
array_diff_assoc($arr1,$arr2,$arr3); Returns an array of difference set results, and the key names are also compared
4. Intersection of arrays
array_intersect($arr1,$arr2); Returns the intersection result array
array_intersect_assoc($arr1,$arr2); Returns the intersection result array, and the key names are also compared
8. Other array functions
range(0,12); Create an array containing the specified range of cells
array_unique($arr); Remove duplicate values ​​in the array, and the original key names will be retained in the new array
array_reverse ($arr,TRUE); Returns an array with the order of cells reversed to the original array. If the second parameter is TRUE, the original key name is retained
//srand((float)microtime()*10000000); Random seed trigger Device
array_rand($arr,2); Randomly remove one or more elements from the array
shuffle($arr); Shuffle the order of the array

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