PHP gets the value set of a column in a two-dimensional array, _PHP tutorial

PHP obtains the value set of a column in a two-dimensional array.

PHP is still relatively commonly used, so I studied PHP two-dimensional arrays. When processing PHP arrays, there is a particularly frequent need, such as the following two-dimensional array:

$arr = array(
1=>array(
'id' => 5,
'name' => '张三'
),
2=>array(
'id' => 6,
'name' => '李四'
)
);

The purpose is to get the set whose key is name and get this result:

$arr2 = array(
0=>'张三',
1=>'李四'
);

Here are several methods:

1: The simplest, foreach traverses the array:

foreach ($arr as $key => $value) {
$arr2[] = $value['name'];
}

2: A slightly smaller code, using the array_map php method:

$arr2 = array_map('array_shift',$arr);

means to remove the value at the beginning of each value of the $arr array, and return the value that was removed from each value. Note that the key of the new array $arr2 is still the original array $arr. The key

2.1: Based on method 2, you can use your imagination a little bit. If you need to get the beginning column or the end column of each item of the two-dimensional array, you can also do this:

$arr2 = array_map('reset',$arr);
$arr2 = array_map('end',$arr);

Haha, it’s also very convenient

3: You can also use the array_reduc e method, but the code is slightly more, but the imagination space of this method (for other array value operations) is still quite large:

$arr2 = array_reduce($arr, create_function('$result, $v', '$result[] = $v["name"];return $result;'));

The array_reduce method uses a callback function to iteratively operate on the values ​​of the array, and create_function is used to make a callback to an anonymous method. The parameter $result of this anonymous method is the value generated by the previous iteration, and $v is the current value. , the internal implementation is to obtain the "name" value of each item in the array $arr and push it to the new $result array;

4: This ultimate method is so cool. It can be done in one method and is very flexible:

$arr2 = array_column($arr, 'name');

The second parameter is the key name of the column you want to get. Isn’t it very convenient? However, this method has a limitation, that is, the PHP version must be >= 5.5.0. This method is still used in old projects. You have to think about it

PS: Several ways to traverse two-dimensional arrays in php

<&#63;php
//使用for循环遍历
$arr2=array(array("张三","20","男"),array("李四","25","男"),array("王五","19","女"),array("赵六","25","女"));
echo "<table border=2 bordercolor=red><tr><td>姓名</td><td>年龄</td& gt;<td>性别</td></tr>";
for($i=0;$i<4;$i++){
echo "<tr>";
for($j=0;$j<3;$j++){
  echo "<td>";
  echo $arr2[$i][$j];
  echo "</td>";
}
echo "</tr>";
echo "<br>";
}
echo "</table>";
&#63;>
//使用foreach遍历
<&#63;php
$arr = array('one'=>array('name'=>'张三','age'=>'23','sex'=>'男'),
  'two'=>array('name'=>'李四','age'=>'43','sex'=>'女'),
  'three'=>array('name'=>'王五','age'=>'32','sex'=>'男'),
  'four'=>array('name'=>'赵六','age'=>'12','sex'=>'女'));
foreach($arr as $k=>$val){
  echo $val['name'].$val['age'].$val['sex']."<br>";
}
echo "<p>";
&#63;>
<&#63;php
$arr = array('one'=>array('name'=>'张三','age'=>'23','sex'=>'男'),
  'two'=>array('name'=>'李四','age'=>'43','sex'=>'女'),
  'three'=>array('name'=>'王五','age'=>'32','sex'=>'男'),
  'four'=>array('name'=>'赵六','age'=>'12','sex'=>'女'));
foreach($arr as $key=>$value){
foreach($value as $key2=>$value2){
  echo $value2;
}
echo "<br>";
}
&#63;>

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