<?php
// Function
/**
* Get the array max depth.
*
* @param array $array
*
* @return int
*/
private function getArrayMaxDepth(array $array): int
{
    $maxDepth = 1;

    foreach ($array as $key => $value) {
        $elementDepth = 2;
        while (is_array($value) === true) {
            foreach ($value as $subValue) {
                if (is_array($subValue) === true) {
                    $elementDepth++;
                    if ($elementDepth > $maxDepth) {
                        $maxDepth = $elementDepth;
                    }
                }
                $value = $subValue;
            }
        }
    }

    return $maxDepth;
}

// Tests

$array1 = [
    // First depth level
    'easy_admin' => [
        //  Second level
        'entities' => [
            // Third level
            'Product' => [
                // Fourth level
                'class' => 'App\Entity\Product'
            ]
        ]
    ]
];

$array2 = [
    'key1-1' => [
        'key1-2' => [
            'key1-3' => [
                'key1-4-1' => 'Not an array, should stop counting here.'
            ]
        ]
    ],
    'key2-1' => [
        'key2-2' => [
            'key2-3' => [
                'key2-4' => [
                    'key2-5' => [
                        'key2-6' => [
                            'key2-7' => 'Not an array, should stop counting here.'
                        ]
                    ]
                ]
            ]
        ]
    ]
];

echo "First array's depth : " . getArrayMaxDepth($array1) . "\n"; // Returns 4 (integer).
echo "Second array's depth : " . getArrayMaxDepth($array2); // Returns 7 (integer).