PHP array learning: change the uppercase or lowercase of keys/values

In the previous article, we introduced the method of deleting any element in the array. If you are interested, you can click on the link to view → "php Array Learning: How to Remove Any Element". This time we will learn how to change the case of array key names or key values ​​in PHP associative arrays. Interested friends can learn about it~

First of all, let’s take a look atHow to change the case of array key names or key values ​​in PHP associative arrays Change the key value to uppercase or lowercase , we have an array like this:

$fruits = array('A' => 'Apple', 'B' => 'Banana', 'c' => 'Cherry', 'o' => 'Orange');

We convert all the array element values ​​​​in it to uppercase:

 $value){
	$fruits[$key]=strtoupper($value);
}
echo "转换为大写后：";
var_dump($fruits);
?>

Use the foreach statement to traverse $fruits array, use the strtoupper($value) function in the loop to convert the array element $value to uppercase, so the output result is:

Conversion Converting to lowercase is similar to converting to uppercase. You only need to replace the strtoupper() function with the strtolower() function. The strtolower() function can convert a string to lowercase.

 $value){
	$fruits[$key]=strtolower($value);
}
echo "转换为小写后：";
var_dump($fruits);
?>

The output result is:

To sum up, encapsulate it into a function that converts upper and lower case:

 $value){
			//如果$case值为CASE_UPPER则，
			if($case==CASE_LOWER){
				$array[$key]=strtolower($value);
			}else if($case==CASE_UPPER){
				$array[$key]=strtoupper($value);
			}
		}
    }
	return $array;
}
$fruits = array('A' => 'Apple', 'B' => 'Banana', 'c' => 'Cherry', 'o' => 'Orange');
$lower=array_change_value_case($fruits,CASE_LOWER);
var_dump($lower);
$upper=array_change_value_case($fruits,CASE_UPPER);
var_dump($upper);
?>

Designarray_change_value_case ($array,$case)The function supports two required parameters $array and $case, where the $case parameter has two values: CASE_LOWER (convert to lowercase letters) and CASE_UPPER (convert to uppercase letters).

Let’s take a look at the above output:

Okay, we already know the key-value conversion method, let’s take a look at the key How to convert a name to uppercase or lowercase ?

Manipulating the case of array key names in PHP is not as complicated as controlling the case of key values ​​above. PHP directly provides a function that converts array key names to uppercase letters or lowercase letters-array_change_key_case(). Let’s take a look at how to use it:

Analysis: array_change_key_case($array ,$case) function supports 1 required parameter $array and 1 omitted parameter $case (control case, default value is CASE_LOWER). $case has two values ​​:

• CASE_LOWER - Default value. Convert an array's keys to lowercase letters.

• CASE_UPPER - Converts an array's keys to uppercase letters.

So the output result is:

Okay, that’s all. If you want to know anything else, you can click this . → →php video tutorial

Finally, I would like to recommend a free video tutorial on PHP arrays: PHP function array array function video explanation, come and learn!

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