I have been working for 4.5 years in my current...

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We would like to inform you that if there is a first contract and a second one and there is no time interval between them, both will be considered as one contract. The end of service indemnity will be calculated on the basis of a total service term equal to the duration of the first employment contract in addition to the duration of the second employment contract. According to the UAE Labor Law, the end of service is calculated on the basis of twenty-one days' salary for each of the first five years of service, and thirty days' wage for each year excesses that.
Here are the texts of the UAE Labor Law related to your inquiry:
Article (38)

 The contract of employment shall be for an indefinite period or for a specified period. If the duration of the contract is specified, it shall not exceed four years. The parties may agree to renew this contract for another similar period or for a period of less than one time or more.  In case of renewing the contract, the new period or periods shall be an extension of the original period and shall be added to the calculation of the total period of service of the worker.

Article 137

 Where a worker under an indefinite term contract abandons his work at his own initiative after a continuous service of not less than one year and not more than three years, he shall be entitled to one-third of the severance pay provided for in the preceding article. Such a worker shall be entitled to two thirds of the said severance pay if his continuous service exceeds three years up to five years, and to the full severance pay if it exceeds five years.

Article 138

 Where a worker under a definite term contract abandons his employment at his own initiative before the expiry of his contract period, he shall not be entitled to severance pay unless his continuous period of service exceeds five years.

Article 139

 A worker shall forfeit entitlement to his entire severance pay in any of the following two cases:

1. If he is dismissed from service for any of the reasons specified in Article 120 hereof or if he abandons his employment in order to avoid being dismissed in accordance with that Article.
2. If he abandons his employment of his own accord, otherwise than in either of the two cases specified in Article 121 hereof, without notice (in the case of indefinite term contracts) or before completing five years of continuous service (in case of definite term contracts).

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