How to add elements to php array

How to add elements to php array

1. array_unshift() inserts new elements into the array head

$fruits = array('apple','pear','banana','orange');
array_unshift($fruits, 'cherry');
    pr($fruits);
function pr($str){    
    echo "<pre class="brush:php;toolbar:false">";    
    print_r($str);    
    echo "

Output:

Array(
    [0] => cherry
    [1] => apple
    [2] => pear
    [3] => banana
    [4] => orange
)

Multiple elements can be passed to array_unshift

$fruits = array('apple','pear','banana','orange');
array_unshift($fruits, 'cherry','pie');
pr($fruits);

Output:

Array(
    [0] => cherry
    [1] => pie
    [2] => apple
    [3] => pear
    [4] => banana
    [5] => orange
)

2. The similar function array_push inserts one or more elements to the end of the array element.

3. array_splice() inserts new elements at any position (regardless of key names)

$fruits = array('apple','pear','banana','orange');
//第三个参数固定为0，第二个参数为插入的索引位置,最后一个参数是插入的元素，如果插入多个，写成数组
array_splice($fruits,3,0,'pie');
pr($fruits);

Output:

Array(
    [0] => apple
    [1] => pear
    [2] => banana
    [3] => pie
    [4] => orange
)

//Insert multiple new elements, written in array form

$fruits = array('apple','pear','banana','orange');$new_items = array('pie','pie2');
array_splice($fruits,3,0,$new_items);
pr($fruits);

Output:

Array(
    [0] => apple
    [1] => pear
    [2] => banana
    [3] => pie
    [4] => pie2
    [5] => orange
)

4. Insert new elements at any position (considering the case of numeric key names)

There is a disadvantage in using array_splice(), it cannot retain numbers. Key name.

There is a known array below

array(7=>'apple',3=>'pear',5=>'banana',2=>'orange');

To insert a new element new fruit after the second element pear, the key name is 6.

The implementation process is a bit tortuous, new The array consists of three parts. See the code for details:

$new_key = 6;
$new_value = 'new fruit';
$exist_value = 'pear';
$array = array(7=>'apple',3=>'pear',5=>'banana',2=>'orange');
$pp = insert_array($array,$exist_value,$new_key,$new_value);
pr($pp);
function insert_array($array,$exist_value,$new_key,$new_value){
    $search_key = array_search($exist_value,array_values($array));
    if($search_key !== false){
        $new_array = array();
        $len = count($array);
        $arr_before = array_slice($array,0,$search_key+1,TRUE);
        $arr_after =$search_key == 0 ? array_slice($array,$search_key,$len,TRUE) : array_slice($array,$search_key-1,$len,TRUE);
        foreach($arr_before as $k=>$v){
            $new_array[$k] = $v;
        }
        $new_array[$new_key] = $new_value;
        foreach($arr_after as $k=>$v){
            $new_array[$k] = $v;
        }
    }else{
        $new_array = $array;
        $new_array[$new_key] = $new_value;
    }
    return $new_array;
}

Recommended tutorial: "PHP Tutorial"

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