How to keep key names the same when merging arrays in PHP

PHP is a powerful open source scripting language used for web development. Among them, array is one of the most commonly used data structures in PHP. In actual development, it is often necessary to merge two or more arrays together. At this time, we often need to keep the key name unchanged to facilitate subsequent operations. This article will explain how to keep key names unchanged when merging arrays in PHP.

The functions for merging arrays in PHP include array_merge() and array_merge_recursive(). array_merge() merges arrays together and returns the merged array. array_merge_recursive() merges two elements with the same key name into an array and returns the merged array. Both functions can merge arrays, but they differ in how they handle elements with the same key.

For example, we have two arrays $a and $b:

$a = array('apple'=>'red', 'banana'=>'yellow', 'orange'=>'orange');
$b = array('apple'=>'green', 'pear'=>'yellow', 'grape'=>'purple');

If we use the array_merge() function to merge these two arrays, the code is as follows:

$c = array_merge($a, $b);

Then, the final result of the merged array $c will be:

array('apple'=>'green', 'banana'=>'yellow', 'orange'=>'orange', 'pear'=>'yellow', 'grape'=>'purple');

As you can see, since only the key-value pairs in the subsequent array are retained after the merge, the key name in $a The element for apple is overwritten by the element with the same key name in $b.

If we use the array_merge_recursive() function to merge the two arrays, the code is as follows:

$c = array_merge_recursive($a, $b);

Then, the final result of the merged array $c will be:

array('apple'=>array('red', 'green'), 'banana'=>'yellow', 'orange'=>'orange', 'pear'=>'yellow', 'grape'=>'purple');

You can see that since elements with the same key name are merged into an array after merging, the element with the key name apple is retained.

However, although the array_merge_recursive() function can keep the key names unchanged, in some cases, we do not want to merge elements with the same key names into an array. For example, if we need to merge two arrays into the same array, and the two arrays contain the same key name, but their values ​​are different, then we need to keep the key name unchanged to facilitate subsequent operations.

So, how to keep the key names unchanged when merging arrays in PHP? A simple and practical way is to use the " " operator. For example, we still use the two arrays $a and $b above, and the code is as follows:

$c = $a + $b;

Then, the final result of the merged array $c will be:

array('apple'=>'red', 'banana'=>'yellow', 'orange'=>'orange', 'pear'=>'yellow', 'grape'=>'purple');

It can be seen that because the " " operator is used, the element with the key name apple in $a is not replaced by the element with the same name in $b, but is retained. In this way, we successfully merged the two arrays and kept their key names unchanged.

Of course, the above method only applies to purely associative arrays. For numeric index arrays, even if the " " operator is used, the key names will change. Therefore, when dealing with numerically indexed arrays, other methods are needed to keep the key names unchanged.

In short, when merging arrays in PHP, you should choose the appropriate function or operator according to different needs to ensure the correctness and efficiency of the operation. When dealing with associative arrays, you can use the " " operator to merge the arrays and keep the key names unchanged.

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