Some commonly used PHP array functions_PHP tutorial

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

http://www.bkjia.com/PHPjc/752530.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/752530.htmlTechArticleProficiency 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...