How to count the number of times a specific key value appears in a two-dimensional array in PHP?

PHP two-dimensional array processing is a common programming task. This article discusses how to efficiently count the occurrence of specific key values ​​in a two-dimensional array.

question:

Given a two-dimensional array, for example:

 $array = [
    ['id' => 1, 'name' => 'a', 'age' => 19],
    ['id' => 2, 'name' => 'b', 'age' => 20],
    ['id' => 3, 'name' => 'c', 'age' => 18],
    ['id' => 5, 'name' => 'd', 'age' => 18],
];

Count the number of subarrays with the 'age' key value of 18.

Solution:

Implementation using foreach loops and counters:

 $array = [
    ['id' => 1, 'name' => 'a', 'age' => 19],
    ['id' => 2, 'name' => 'b', 'age' => 20],
    ['id' => 3, 'name' => 'c', 'age' => 18],
    ['id' => 5, 'name' => 'd', 'age' => 18],
];

$count = 0;
foreach ($array as $item) {
    if ($item['age'] === 18) {
        $count ;
    }
}

echo "There are 18 years old" . $count . " . " ; // Output: There are 2 people with 18 years old.

The code first initializes the counter $count to 0. foreach loops through each subarray. The if statement checks whether the value of the 'age' key is equal to 18. If so, $count is added 1. Finally, output the result. This method is simple and efficient, easy to understand and modify to count other key values. Note that the strict comparison operator === is used here to ensure that the data types are consistent.

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