Example analysis of common array functions in PHP

This article mainly introduces the commonly used array functions in PHP. It summarizes and analyzes the functions and usage skills of PHP's commonly used array functions array_merge, array_slice and array_map in the form of examples. Friends in need can refer to the following.

The details are as follows:

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

Function function: Merge an or The cells of multiple arrays are combined, and the values ​​in one array are appended to the previous array. Returns an array of results.

If the input array has the same string key name, 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 subsequent 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: Returns a sequence in the array specified by the offset and length parameters.

If offset is non-negative: the array will start from the offset from the beginning 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 from the offset from the end to offset. array_slice($array,-2); Equivalent to (1,2,3,4,5,6);

If length is positive: from offset The starting number of interceptions. array_slice($array,2,2); Equivalent to (1,2,3,4,5,6);

If length is negative: then The sequence will terminate this far from the end of the array; array_slice($array,2,-1); is equivalent to (1,2,3,4,5 ,6);
The default is: to the end of the array.

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.

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

Output:

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

The above is the summary of this article All content, I hope it will be helpful to everyone's study.

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