Summary of common array function usage in PHP_php tips

The examples in this article describe the usage of common array functions in PHP. Share it with everyone for your reference, the details are as follows:

1.array array_merge(array $array1 [, array $array2 [, $array]])

Function: Combine the cells of one or more arrays, and the values ​​in one array are appended to the previous array. Returns an array of results.

If there is the same string key name in the input array, the value after the key name will overwrite the previous value. However, if the array contains numeric keys, the subsequent values ​​will not overwrite the original values ​​but will be appended to them.

If only an array is given and the array is numerically indexed, the key names are re-indexed in a consecutive manner.

Example 1: There are the same string key names in the array

$array1=array('color'=>'greed','3'=>8);
$array2=array("a",'color'=>"red",'3'=>8);
var_dump(array_merge($array1,$array2));

Output:

array(4){
  ["color"]=> string(3) "red"
  [0]=> int(8)
  [1]=> string(1) "a"
  [2]=> int(8)
}

The color with repeated key names is overwritten, and only the following value 'red' is taken, while the '3' with the same numerical key name is not overwritten, but appended to the end.

2.array array_slice(array $array,int $offset, [, int $length [, bool $preserve_keys ]])

Function function: Return a sequence in the array specified by the offset and length parameters.

If offset is non-negative: the array will start at the offset from the start end to offset. $array=array(1,2,3,4,5,6); array_slice($array,2); equivalent to (1,2,3,4,5,6); red represents the intercepted array
If offset is negative: the array will start at an offset from the end to offset. array_slice($array,-2); equivalent to (1,2,3,4,5,6);
If length is positive: the number of interceptions starting from offset. array_slice($array,2,2); equivalent to (1,2,3,4,5,6);
If length is negative: the sequence will terminate this far from the end of the array; array_slice($array,2,-1); equivalent to (1,2,3,4,5,6);
Default: to the end of the array.

For specific usage of array_slice, you can also refer to the previous article on this site " Detailed explanation of usage examples of array_slice function in PHP "

3.array_map(callback $callback , array $arr1[, array $.....])

Function function: Return an array that contains all units in arr1 after callback has been applied. The number of arguments accepted by callback should match the number of arrays passed to the array_map() function.

<&#63;php
function cube($n)
{
  return($n * $n * $n);
}
$a = array(1, 2, 3, 4, 5);
$b = array_map("cube", $a);
print_r($b);
&#63;>

Output:

Array
(
  [0] => 1
  [1] => 8
  [2] => 27
  [3] => 64
  [4] => 125
)

Readers who are interested in more PHP-related content can check out the special topics on this site: "Summary of PHP operating office document skills (including word, excel, access, ppt)", "php date Time usage summary", "php object-oriented programming introductory tutorial", "php string (string) usage summary", "php mysql database operation Introductory tutorial " and " Summary of common PHP database operation skills "

I hope this article will be helpful to everyone in php programming.