Introduction to the use of PHP array_map() function

PHP array_map() function usage introduction

The array_map() function in PHP is an array processing function that can traverse one or more arrays and apply the specified function to each element to generate a new array. This article will introduce the syntax, parameters, return value, usage and precautions of the array_map() function.

Syntax:

array_map ( callable $callback , array $array1 [, array $...] ) : array

Parameters:

callback: Required. Specifies how each element in the array should be mapped.

array1: required. Specifies the array to be mapped.

...: Optional. Optional array, any number of arrays can be used in a function call. These arrays will be processed simultaneously, that is, the first element in the returned array is the first element from the first array, the second element is from the first element of the second array, and so on.

Return value:

The array_map() function returns an array containing the mapping results of the elements in each array passed to the function.

Usage:

The first parameter callback in this function can be a function name or an anonymous function to be applied to each element in the array.

Example 1: Use function name as callback function

// Define callback function
function myFunction($value)
{
return $value * 2;
}

// Define the array
$a = array(1, 2, 3, 4, 5);

// Apply the callback function For each element in the array
$b = array_map("myFunction", $a);

//Output result
print_r($b);
?>

Output result:

Array ( [0] => 2 [1] => 4 [2] => 6 [3] => 8 [4] => 10 )

Example 2: Using anonymous function as callback function

// Define array
$a = array(1, 2, 3, 4, 5 );

//Apply anonymous function to each element in the array
$b = array_map(function($value) { return $value 1; }, $a);

//Output result
print_r($b);
?>

Output result:

Array ( [0] => 2 [1] => ; 3 [2] => 4 [3] => 5 [4] => 6 )

Example 3: Apply callback functions to multiple arrays at the same time

// Define array
$a = array(1, 2, 3, 4, 5);
$b = array(6, 7, 8, 9, 10);

//Apply callback function to each element in both arrays
$c = array_map(function($value1, $value2) { return $value1 $value2; }, $a, $b);

//Output result
print_r($c);
?>

Output result:

Array ( [0] => 7 [1 ] => 9 [2] => 11 [3] => 13 [4] => 15 )

Notes:

1. If there is an If the item is NULL, the corresponding item in the returned new array is also NULL.

2. If the array element passed to the callback function is greater than one, the value of each element will be passed to the callback function as a parameter.

3. If the number of parameters passed to the callback function is less than the number of array elements, the parameters of each callback function will be set to NULL.

To sum up, the PHP array_map() function is a very practical array processing function that can easily map elements in an array and generate a new array. When using, pay attention to the settings of parameters and callback functions to achieve the desired effect.

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