How to add new element to beginning of associative array in PHP?

In PHP, an associative array is an array type where the indexes do not need to be as strictly ordered as indexed arrays. Usually when adding a new element to an existing associative array, it will be appended to the end of the array.

Example:

<?php 
  
$arr = array(&#39;one&#39; => 1, &#39;two&#39; => 2); 
$arr[&#39;zero&#39;] = 0; 
print_r($arr); 
  
?>

Output:

Array
(
    [one] => 1
    [two] => 2
    [zero] => 0
)

Therefore, new elements cannot be added directly to the beginning of an associative array, but to an existing array Can be appended to the end of a new array, where the first element is the new element.

This means that adding a new element at the beginning first requires placing the new element as the first element into an empty array, and then the array needs to be merged with the existing array. In PHP, there are two ways to merge arrays, they are the array_merge() function or you can use the array union() operator.

In the case of the array_merge() function, if two arrays have the same key, the value corresponding to the key in the latter array is considered in the resulting array. But in case of indexed array, elements are just appended and all elements in the resulting array are re-indexed.

Syntax:

array array_merge( $arr1, $arr2 )

The code example is as follows:

<?php 
$arr = array(&#39;one&#39; => 1, &#39;two&#39; => 2, &#39;three&#39; => 3);          
$temp = array(&#39;zero&#39; => 0); 
      
$arr2 = $temp + $arr;       
print_r($arr2); 
      
$arr3 = array_merge($temp, $arr);       
print_r($arr3);

Output:

Array
(
    [zero] => 0
    [one] => 1
    [two] => 2
    [three] => 3
)

Array
(
    [zero] => 0
    [one] => 1
    [two] => 2
    [three] => 3
)

Related recommendations: "PHP Tutorial"

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