crash.php

<?php

namespace App\Models;

class PhpVersionCollection implements \Countable, \ArrayAccess, \JsonSerializable, \IteratorAggregate
{
    /** @var array */
    private $versionNumbers = ['5.6', '7.0', '7.1', '7.2', '7.3'];


    /**
     * Determine if the validation rule passes.
     *
     * @param  string  $attribute
     * @param  mixed  $value
     * @return bool
     */
    public function passes($attribute, $value)
    {
        return $this->exists($value);
    }


    /**
     * Get the validation error message.
     *
     * @return string
     */
    public function message()
    {
        return 'Please choose a valid PHP version';
    }


    /**
     * Check if an arbitrary string is a valid PHP version number
     *
     * @param string $version
     *
     * @return bool
     */
    public function exists($version)
    {
        return $this[$version] ? true : false;
    }

    /**
     * jsonSerialize
     *
     * @return array
     */
    public function jsonSerialize()
    {
        return [
            'versions' => $this->versionNumbers
        ];
    }

    public function offsetSet($k, $v)
    {
        throw new \RuntimeException('Cannot set a value at index because this is a read only collection');
    }

    public function offsetExists($key)
    {
        return in_array($key, $this->versionNumbers);
    }

    public function offsetUnset($key)
    {
        throw new \RuntimeException('Cannot unset an index because this is a read only collection');
    }

    public function offsetGet($key)
    {
        return $this[$key] ?? null;
    }

    public function count()
    {
        return \count($this->versionNumbers);
    }

    /**
     * Undocumented function
     *
     * @return \ArrayIterator
     */
    public function getIterator()
    {
        return new \ArrayIterator($this->versionNumbers);
    }
}

$crasher = new PhpVersionCollection();

var_dump($crasher->exists('7.2'));