Introduction to how to delete null values ​​in an array in PHP_PHP Tutorial

Ashamed to say, in the past, when removing empty values ​​from an array, foreach or while were forced. Use these two syntax structures to delete empty elements in the array. The simple code is as follows:

Copy code The code is as follows:

foreach( $arr as $k=>$v){
if( !$v )
unset( $arr[$k] );
}
?>

And I feel pretty good about it, but it’s not very efficient. I’ve tried it before, first converting $arr to an object, and then using the characteristics of the object to delete it, because: foreach copies the currently operated array. Every time you operate foreach, a variable is copied. If there are too many foreach on the page, it will be a big waste.

When I was wandering around on the Internet, I was surprised to see people suggesting using array_filter. I opened the manual and took a look, and found that I had been guarding a treasure mountain but didn't know how to use it.

The function of the array_filter function is to use the callback function to filter the array. I always thought that the callback function can be used to process it, but I didn’t find that there is another sentence in the manual. If there is no callback function, then the default is to delete the array whose value is false. project.

Copy code The code is as follows:

$entry = array(
0 => 'foo',
1 => false,
2 => -1,
3 3 => null,
4 > ''
);

print_r(array_filter($entry)); >
The code is as follows:

Array
(

[0] => foo [2] => -1 )

It seems that I still need to read the manual more in the future...just like array_slice, it is also a good thing. Too bad I never noticed it before.


Attachment: Another example

Copy code

The code is as follows:$strDelCodes = "A;B;;C;;C;D;;;D;D ";

$rsArray = array_values ​​(array_unique (array_diff (split (";", $strDelCodes), array (""))));

The values ​​stored in the array $rsArray are: A B C D array_values() function returns an array containing all key values ​​in the given array, but does not retain the key names.

The array_diff() function returns the difference array of two arrays. This array contains all keys that are in the array being compared, but are not in any of the other argument arrays.

array_unique() function removes duplicate values ​​from an array and returns the resulting array. When the values ​​of several array elements are equal, only the first element is retained and the other elements are deleted.

The key names in the returned array remain unchanged.

The array_merge() function merges two or more arrays into one array.

If there are duplicate key names, the key value of the key will be the value corresponding to the last key name (the later one will overwrite the previous one). If the array is numerically indexed, the key names are re-indexed consecutively.

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TechArticleI am ashamed to say that in the past, when removing the null value of an array, I always forced to write foreach or while. Use these two A syntax structure to delete empty elements in the array, the simple code is as follows: Copy code generation...