PHP gets an instance of a specified column in an array

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For a multi-dimensional array (taking a two-dimensional array as an example), it is often necessary to obtain one of the columns. For example, there are several pieces of user data, which is a two-dimensional array. Now we need There are many ways to get the names of these users:

$arr = array(
	array(
		'id'=>'101',
		'name'=>'qu',
		'age'=>28
	),
	array(
		'id'=>'102',
		'name'=>'you',
		'age'=>24
	),
	array(
		'id'=>'103',
		'name'=>'zheng',
		'age'=>22
	),
	array(
		'id'=>'104',
		'name'=>'zhu',
		'age'=>23
	)
);

Method 1: Use the PHP built-in function array_column( )Achieve

array array_column ( array $input , mixed $column_key [, mixed $index_key ] )

Execution statement:

$result = array_column($arr,'name')； 
print_r($result);

The results are as follows:

Array 
( 
 [0] => qu 
 [1] => you 
 [2] => zheng 
 [3] => zhu 
)

If the optional parameter index_key is specified, then the value of this column in the input array Will serve as the key to the corresponding value in the returned array.

$result = array_column($arr,'name','id'); 
print_r($result);

The results are as follows:

Array 
( 
 [101] => qu 
 [102] => you 
 [103] => zheng 
 [104] => zhu 
)

Method 2: Use PHP built-in function array_map() to implement

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

array_map() returns an array that contains All units in arr1 are units after callback has been applied. The first parameter is a callback function, and the return value is an array. Each element of the array is processed by the callback function (callback).

First declare a processing function:

function get_val($arr){ 
 return $arr['name']; 
}

Then act on the array_map() function:

$result = array_map('get_val',$arr); 
print_r($result);

The execution results are as follows:

Array 
( 
 [0] => qu 
 [1] => you 
 [2] => zheng 
 [3] => zhu 
)

This The first parameter of array_map() is a callback function, and it is a well-known function defined in advance. Here we can also use anonymous functions like js:

$result = array_map(function($v){ 
 return $v['name']; 
},$arr);

The execution results are the same.

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