The difference in usage between array_map function and array_walk function in php

The content of this article is about the usage difference between array_map function and array_walk function in PHP. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

array_map():
1. The array_map() function applies the user-defined function to each value in the array and returns the band after the user-defined function is applied. For an array with new values, if there is no return value after the function is applied, the corresponding new value array will be empty.
2. The number of parameters accepted by the callback function should be consistent with the number of arrays passed to the array_map() function.
3. Tip: You can input one or more arrays to the function.

If the phase function inputs two arrays, its function should also accept two parameters. When map passes a value to the function, it takes one from the two arrays each time and passes it to the function
. That is, multiple arrays are submitted synchronously. Instead of submitting one array and then submitting the next one
Submitting several arrays, the function also needs to have several parameters

4. Syntax: array array_map (callable arr1 [, array $… ] )

Example:

<?php //单数组形式
function myfunction($v){
    if ($v==="Dog")
    {        
    return "Fido";
    }    
    return $v;
}
$a=array("Horse","Dog","Cat");
print_r(array_map("myfunction",$a));//多数组形式
function myfunction1($v1,$v2){
    if ($v1===$v2)
    {        
    return "same";
    }    
    return "different";
}
$a1=array("Horse","Dog","Cat");
$a2=array("Cow","Dog","Rat");
print_r(array_map("myfunction1",$a1,$a2));
?>

array_walk():
1. array_walk - Use user-defined functions to perform callback processing on each element in the array
2. Syntax: bool array_walk ( array &

funcname [, mixed $userdata = NULL ] )

Parameters:

$array Input array. $funcname callback function, typically $funcname accepts two parameters.

$array The value of the parameter is used as the first one, and the key name is used as the second one.

$userdata If the optional parameter $userdata is provided, it will be passed to $funcname as the third parameter.

Note:

If $funcname needs to act directly on the values ​​in the array, specify the first parameter of funcname as a reference (add the & symbol ). In this way
Any changes to these cells will also change the original array itself.

Return value:

Returns TRUE on success, or FALSE on failure.

Example:

<?php
$fruits = array("d" => "lemon", "a" => "orange", "b" => "banana", "c" => "apple");//传引用，改变了所传参数组
function test_alter(&$item1, $key, $prefix){
    $item1 = "$prefix: $item1";
}function test_print($item2, $key){
    echo "$key. $item2<br />\n";
}echo "Before ...:\n";//单数组
array_walk($fruits, &#39;test_print&#39;);//带额外参数
array_walk($fruits, &#39;test_alter&#39;, &#39;fruit&#39;);
echo "... and after:\n";
array_walk($fruits, &#39;test_print&#39;);

The above routine will output:

Before ...:
d. lemon
a. orange
b. banana
c. apple ... and after:
d. fruit: lemon
a. fruit: orange
b. fruit: banana
c. fruit: apple

Key points:

map is mainly to get the new array processed by your callback function. What you want is the result.

walk The main thing is to use your callback function once for each parameter. What is important is the processing process.

walk can be considered to provide additional parameters to the callback function, but map cannot.

walk is mainly to operate on each value in the array, and the operation result affects the original array map. It is mainly to operate on the array. Return the array after operating on the values ​​in it to get a new array

walk There is no need to return a value map because the array needs to be filled

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