Function to validate a data array using a schema

schema.php

<?php

/* Validation schema example */
$schema = [
    'id' => ['field' => 'id'],
    'name' => [
        'field' => 'name',
        'required' => true,
        'validation' => ['type' => 'string']
    ],
    'username' => [
        'field' => 'username',
        'required' => true,
        'validation' => [
            'type' => 'string',
            'length' => [6, 12]
        ]
    ],
    'age' => [
        'field' => 'age',
        'validation' => [
            'filter' => FILTER_VALIDATE_INT,
            'options' => ['min_range' => 18, 'max_range' => 99]
        ]
    ],
    'phone' => [
        'field' => 'phone',
        'validation' => ['regex' => '/^[0-9]{3}-[0-9]{3}-[0-9]{4}$/']
    ],
    'email' => [
        'field' => 'email',
        'required' => true,
        'validation' => ['filter' => FILTER_VALIDATE_EMAIL]
    ]
];

?>

validation.php

<?php

function validateParameters($parameters, $schema) {
    $all_errors = [];
    $validated = array_map(function($parameter, $options) use (&$parameters, &$all_errors) {
        $errors = [];
        $value = $parameters[$parameter];
        if ($value === null) {
            if ($options['required']) $all_errors[] = $parameter.' is required';
            return null;
        }
        unset($parameters[$parameter]);
        if ($options['validation']) {
            $valid = $options['validation'];
            if ($valid['filter'] && !filter_var($value, $valid['filter'], ['options' => $valid['options']])) $errors[] = $parameter.' value is invalid';
            if ($valid['type'] && gettype($value) !== $valid['type']) $errors[] = $parameter.' value is invalid';
            if ($valid['regex'] && !preg_match($valid['regex'], $value)) $errors[] = $parameter.' value is invalid';
            if ($valid['length'] && !inBetween(strlen($value), $valid['length'])) $errors[] = $parameter.' is too short/long';
        }
        $all_errors = array_merge($all_errors, $errors);
        return count($errors) ? null : $options['field']. ' = :'.$parameter;
    }, array_keys($schema), $schema);
    if (count($parameters)) $all_errors[] = 'invalid parameter(s) '.implode(', ', array_keys($parameters));
    return [
        'parameters' => array_values(array_filter($validated)),
        'errors' => $all_errors
    ];
}

function inBetween($val, $range) {
    return is_array($range) ? $val >= $range[0] && $val <= $range[1] : $val === $range;
}

?>