Expert PHP Developer Needed: Core PHP 8.3 Architecture Unification (Strict Single Codebase & CSS Logical Properties)

### Project Description:
B2B corporate established platform built on Custom Core PHP 8.3.
(Important Note: The upgraded PHP 8.3 logic and modern features like WhatsApp integration exist ONLY within our current Arabic files).

Needed an expert Backend/Frontend developer to take this updated Arabic codebase as the ONLY root engine and refactor it into a strict Single Codebase
(Zero Code Duplication). This unified codebase must dynamically serve two distinct domains (egyptmart.com for Arabic/RTL and arab-mart.com for English/LTR).

### Key Architectural Requirements:
1. Dynamic Routing & Core Unification: Implement a centralized routing mechanism to detect the incoming domain and dynamically switch languages, database configurations, and UI directions using a SINGLE set of core files.

2. Dynamic Database Mapping: The platform utilizes parallel tables for different languages (e.g., 'business_profile' for Arabic and 'business_profile_arabyos' for English). You must implement a centralized SQL rewrite layer/mapping logic in the configuration so that all existing database queries automatically route to the correct table based on the active domain without duplicating the query paths across files.

3. Internationalization (I18n): Cleanly extract all hardcoded UI strings from the core Arabic files into dedicated language files ('lang/ar.php'). You will extract the English translation strings from our legacy English files and place them into 'lang/en.php'.

4. Modern CSS Mirroring (Strict): You must refactor the stylesheet using "CSS Logical Properties" (e.g., margin-inline, padding-inline, start/end) so one single stylesheet dynamically handles both LTR and RTL layouts. Creating separate RTL overlay files or manual "page flipping" is strictly prohibited.

5. Preservation of Core Logic: Existing functional logic, background scripts, and automation cron-jobs in the root directory must remain fully operational.
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### Security, Testing & Delivery Terms
1. Isolated Staging Environment: All deployment and testing will happen inside an isolated staging directory on our Hostinger server. Restricted FTP access will be provided. No live/primary database access will be shared; you must provide the SQL alteration scripts for us to execute on our end.
2. Code Duplication Audit: The final delivery will undergo a strict source code audit. If any duplicated files or separate LTL/RTL stylesheets are found, the delivery will be rejected.
3. Deadline: Maximum of 5 consecutive calendar days for full implementation.

### Sequential Milestone & Payment Terms (Final Release Upon Full Completion)
IMPORTANT: No milestone will be released individually during the project, the project budget is divided into 3 sequential milestones. :
* Milestone 1 (40% of Budget) - Funded immediately upon project award:
This is the ONLY milestone funded (escrowed) at the start. It will NOT be released until the entire project is completed.
This phase covers: establishing the upgraded Arabic PHP 8.3 files as the single codebase on our subdomain (m.egyptmart.shop/m/), connecting the two-domain routing config, integrating ar.php / en.php into the agreed frontend pages, completing the necessary CSS/JS/LTR-RTL adjustments to a clean standard.

* Milestone 2 (30% of Budget) - Funded ONLY after Phase 1 is verified on the server:
This milestone remains UNFUNDED (no escrow) at the start. It will be funded in the dashboard only after Phase 1 is deployed and visually verified. Once funded, it will NOT be released. This phase covers: Full English text extraction from legacy files and complete Arabic text organization for the agreed frontend pages.

* Milestone 3 (30% of Budget) - Same as previous milestone 2, (no escrow) until Phase 2 is completed. Once funded, it covers: Final thorough review, bug fixes, and stable operational testing on the subdomain.

FINAL RELEASE CONDITION:
**The total project budget (100% across all 3 milestones) will be released to the freelancer ONLY after our management performs a full source-code audit on our Hostinger server, confirms Zero Code Duplication, verifies dynamic database mapping, and officially signs off on the flawless functionality of both domains. tested, and approved on our staging server. .
**Time Deadline: within maximum 6 consecutive calendar days.

If you are a senior developer who stands behind the quality of your code and accepts these transparent structural terms, please apply with your exact timeframe.