獲取二維數組中指定字段的值，而且將值組成一維數組

從數據庫獲取多個數據時每每是二維數組，可是有時候咱們須要獲取數組裏面的某一鍵的數據。有兩種方法：foreach()循環和Array()函數

示例數組，獲取二維數組裏面的device_token的值而且放在一維數組裏面：

$arr = array(
 0 => array(
 'device_token' => 'AnBWyVMD1u0qKkNrD44h8BaFjROX5qCRgDjEG6CCFtFd',
 'shebei' => 'android'
 ),
 1 => array(
 'device_token' => 'Ap0pTms6pvxMtsvrqCvzbqknLkO6KEIJnk3x9iGYlgd8',
 'shebei' => 'android'
 ),
 2 => array(
 'device_token' => '6aa7d1356e75a56758a0fdc40b776d0cab7fa8889de546106888d3b3c5eee872',
 'shebei' => 'ios'
 ),
 3 => array(
 'device_token' => '9e9854b6b6f02c58aa8838619b25e18139558dca9f69e2abbc6f9b88630ff269',
 'shebei' => 'ios'
 ),
 4 => array(
 'device_token' => 'ApKqVYFWWXNds9CnveE24ysTZ942nw5P2o5lE6KJegqg',
 'shebei' => 'android'
 ),
 5 => array(
 'device_token' => '',
 'shebei' => 'ios'
 ),
　　6 => array(
　　　　'device_token' => 0,
　　　　'shebei' => 'android'
　　)
);

1、foreach()循環

$IOS_token = array();
$android_token = array();
if(!empty($arr) && count($res) != 0){
 foreach($arr as $key => $val){
 if($val['shebei'] == 'android'){
 $android_token[] = $val['device_token'];
 }elseif($val['shebei'] == 'ios'){
 $IOS_token[] = $val['device_token'];
 }
 }
}

2、Array()函數

$ios_res = array_column(array_filter($arr,function($val){
 if($val['shebei'] == 'ios'){
 return $val['device_token'];
 }else{
 return false;
 }
}),'device_token');
$android_res = array_column(array_filter($arr,function($value){
 if($value['shebei'] == 'android'){
 return $value['device_token'];
 }else{
 return false;
 }
}),'device_token');

返回結果一維數組：

Array ( [ios] => Array ( [0] => 6aa7d1356e75a56758a0fdc40b776d0cab7fa8889de546106888d3b3c5eee872 [1] => 9e9854b6b6f02c58aa8838619b25e18139558dca9f69e2abbc6f9b88630ff269 ) [android] => Array ( [0] => AnBWyVMD1u0qKkNrD44h8BaFjROX5qCRgDjEG6CCFtFd [1] => Ap0pTms6pvxMtsvrqCvzbqknLkO6KEIJnk3x9iGYlgd8 [2] => ApKqVYFWWXNds9CnveE24ysTZ942nw5P2o5lE6KJegqg ) )

原始數組$arr中ios其實有三個，可是有一個是空值，因此array_filter()函數給過濾掉了；android分類下的0也被過濾掉了。

注意點：array_filter會過濾掉任何等於FALSE的值，也就是說  0值，空字符串，null，都會被過濾