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+# mPDF Reference — HMS E-Atria Project
+
+Source: https://mpdf.github.io/
+Version used: mpdf/mpdf (composer, see vendor/)
+
+---
+
+## 1. Core Pattern — Single WriteHTML Call (used in this project)
+
+mPDF does NOT require a full HTML document (`<!doctype>`, `<html>`, `<head>`, `<body>`).
+Pass a plain HTML fragment to `WriteHTML()`.
+
+### Correct structure for a templated PDF with header/footer:
+
+```
+<style>
+@page {
+    margin-top: 3cm;
+    margin-bottom: 2cm;
+    margin-left: 0.8cm;
+    margin-right: 0.8cm;
+    margin-header: 1cm;
+    margin-footer: 0.5cm;
+    header: html_myHeader;   /* activates the named header on every page */
+    footer: html_myFooter;
+}
+
+body {
+    font-family: DejaVu Sans, sans-serif;
+    font-size: 11pt;
+}
+table { width:100%; border-collapse: collapse; }
+th, td { border: 1px solid #000; padding: 6px; }
+</style>
+
+<htmlpageheader name="myHeader">
+    <div style="text-align:center; font-weight:bold;">Hospital Name</div>
+    <hr>
+</htmlpageheader>
+
+<htmlpagefooter name="myFooter">
+    <div style="text-align:right; font-size:9pt;">Page {PAGENO} of {nbpg}</div>
+</htmlpagefooter>
+
+<h1>Discharge Summary</h1>
+<p>Patient content here…</p>
+```
+
+**Rules:**
+- `@page` block MUST be in a `<style>` tag placed BEFORE the named header/footer blocks.
+- `header: html_myHeader;` in `@page` binds the named block to every page.
+- Named headers use `html_` prefix when referenced from `@page` / `AddPage()`.
+- Do NOT name any header/footer starting with `html_` when defining it — the prefix is reserved for referencing only.
+- `margin-header` = space between the top of the physical page and the top of the header content.
+- `margin-top` = space between the bottom of the header and the start of the body content.
+
+---
+
+## 2. PHP Constructor (new Mpdf\Mpdf([...]))
+
+```php
+$mpdf = new Mpdf([
+    'mode'          => 'utf-8',
+    'format'        => 'A4',          // A4, A4-L, A5, A6, LETTER, LEGAL, or [width_mm, height_mm]
+    'margin_top'    => 30,            // mm — used as fallback if no @page CSS
+    'margin_bottom' => 20,
+    'margin_left'   => 8,
+    'margin_right'  => 8,
+    'margin_header' => 10,            // mm — space reserved for header
+    'margin_footer' => 5,
+    'default_font'  => 'freeserif',   // project default for Hindi/Unicode support
+    'tempDir'       => WRITEPATH . 'cache',
+    'autoScriptToLang' => true,       // required for Hindi/Devanagari
+    'autoLangToFont'   => true,
+]);
+```
+
+If `@page` CSS is present, CSS margins override the constructor margins.
+The constructor `format` always controls the page size (not settable via `@page`).
+
+---
+
+## 3. Named HTML Header/Footer — Method 4 (recommended)
+
+**Define** using custom HTML tags in the WriteHTML content:
+```html
+<htmlpageheader name="myHeader">
+    <div>Header content with {PAGENO} {DATE j-m-Y}</div>
+</htmlpageheader>
+```
+
+**Activate** using `@page` in `<style>`:
+```css
+@page {
+    header: html_myHeader;   /* Note: "html_" prefix ONLY in reference, not in name="" */
+    footer: html_myFooter;
+}
+```
+
+**Alternative activate** via PHP (for runtime change):
+```php
+$mpdf->SetHTMLHeaderByName('myHeader');
+$mpdf->SetHTMLFooterByName('myFooter');
+```
+
+**Dynamic variables inside headers/footers:**
+- `{PAGENO}` — current page number
+- `{nbpg}` — total number of pages
+- `{DATE j-m-Y}` — date formatted using PHP date() format
+
+---
+
+## 4. Output Methods
+
+```php
+// Inline (stream to browser)
+$mpdf->Output('filename.pdf', 'I');
+
+// Download
+$mpdf->Output('filename.pdf', 'D');
+
+// Save to file
+$mpdf->Output('/path/to/file.pdf', 'F');
+
+// Return as string (used in this project)
+$binary = $mpdf->Output('filename.pdf', \Mpdf\Output\Destination::STRING_RETURN);
+```
+
+---
+
+## 5. Page Numbers / Date in Footers
+
+```html
+Page {PAGENO} of {nbpg}         — recommended
+Page {PAGENO}/{nb}              — also works
+Date: {DATE d-m-Y}
+```
+
+Set alias for {nb}:
+```php
+$mpdf->AliasNbPages('{nbpg}');  // optional, default is {nbpg}
+```
+
+---
+
+## 6. Supported CSS — Key Properties
+
+### @page selector
+```css
+@page {
+    size: A4;                        /* sets page size (alternative to constructor format) */
+    margin-top: 3cm;
+    margin-bottom: 2cm;
+    margin-left: 0.8cm;
+    margin-right: 0.8cm;
+    margin-header: 1cm;
+    margin-footer: 0.5cm;
+    header: html_myHeader;          /* HTML named header (use html_ prefix) */
+    footer: html_myFooter;
+    odd-header-name: html_myHeader; /* alternative: for odd pages only */
+    odd-footer-name: html_myFooter;
+}
+@page :first { ... }               /* first page only */
+@page :right { ... }               /* right/odd pages */
+@page :left  { ... }               /* left/even pages */
+@page named  { ... }               /* named page selector, activated by page: named; on a block */
+```
+
+### Units supported
+`px`, `pt`, `cm`, `mm`, `in`, `em`, `rem`, `ex`, `%`
+
+### Not supported
+- CSS Grid, Flexbox
+- CSS Variables (--custom-property)
+- Most CSS3 transitions/animations
+- `position: sticky`, `position: relative` (only `fixed` and `absolute` supported)
+
+---
+
+## 7. Fonts — Hindi / Devanagari (used in discharge medicines)
+
+For Hindi text (dose descriptions like "हर दो घंटे पर"):
+
+```php
+$mpdf = new Mpdf([
+    'default_font'     => 'freeserif',
+    'autoScriptToLang' => true,
+    'autoLangToFont'   => true,
+]);
+```
+
+`freeserif` is bundled with mPDF and contains Devanagari glyphs.
+For better rendering use `dejavusans` or configure a custom font.
+
+Custom font example:
+```php
+$mpdf = new Mpdf([
+    'fontDir'  => [__DIR__ . '/fonts'],
+    'fontdata' => $defaultFontData + [
+        'myfont' => ['R' => 'MyFont-Regular.ttf'],
+    ],
+    'default_font' => 'myfont',
+]);
+```
+
+---
+
+## 8. Images in Headers
+
+For images in `<htmlpageheader>`, use absolute server path:
+```html
+<htmlpageheader name="myHeader">
+    <img src="/var/www/html/hms_etria/public/assets/images/logo.png" style="width:80px;">
+</htmlpageheader>
+```
+
+Do NOT use relative paths or `url()`. The `{{H_logo_abs}}` token in this project
+resolves to `FCPATH . 'assets/images/' . $hLogo`.
+
+---
+
+## 9. Tables in PDF
+
+```html
+<table width="100%" border="0" cellpadding="4" cellspacing="0">
+    <thead>
+        <tr style="background:#f2f2f2;">
+            <th>Medicine</th><th>Dose</th><th>Days</th>
+        </tr>
+    </thead>
+    <tbody>
+        <tr><td>Paracetamol</td><td>1 tab BD</td><td>5</td></tr>
+    </tbody>
+</table>
+```
+
+- Use `border-collapse: collapse` in CSS for clean borders.
+- `border="0"` attribute overrides CSS borders — use CSS instead.
+- Tables are not CSS `display:table` — they use mPDF's own table engine.
+
+---
+
+## 10. How Discharge PDF is Built in This Project
+
+File: `app/Controllers/Ipd_discharge.php` — method `show_discharge()`
+
+```
+1. Load template settings from ipd_discharge_templates (id = requested ?tpl=N or is_default=1)
+2. Read / auto-generate discharge content (token-replaced template_html)
+3. Build mPDF constructor with: format, margins (all from template settings)
+4. Build WriteHTML fragment:
+     <style>@page { margins; header: html_myHeader; }</style>
+     <style>template_css</style>
+     <htmlpageheader name="myHeader">header_html (tokens replaced)</htmlpageheader>
+     <htmlpagefooter name="myFooter">footer_html (tokens replaced)</htmlpagefooter>
+     rendered template body (template_html with tokens replaced)
+5. $mpdf->WriteHTML($pdfHtml)
+6. Output as binary PDF string → CI4 response
+```
+
+**Token replacement**: `{{TOKEN_NAME}}` or `{{token_name}}` — case-insensitive.
+Available tokens: H_Name, H_logo_abs, PATIENT_NAME, UHID, IPD_CODE, ADMIT_DATE,
+DISCHARGE_DATE, FINAL_DIAGNOSIS, SURGERY, DISCHARGE_MEDICATIONS, DISCHARGE_SUMMARY,
+CONTENT (all sections), and many more — see placeholder list in template editor.
+
+**Debug**: `/Ipd_discharge/show_discharge/{ipdId}/1?tpl={tplId}&html=1`
+Shows the exact HTML string passed to `WriteHTML()`.
+
+---
+
+## 11. Common Issues and Fixes
+
+| Problem | Cause | Fix |
+|---|---|---|
+| Header not repeating on every page | Missing `header: html_myHeader` in `@page` | Add `header: html_myHeader;` to `@page` block in CSS textarea |
+| CSS appears as visible text | CSS injected inside body `<div>`, not in `<style>` before content | Put all CSS in template CSS field; system puts it in `<style>` |
+| `{PAGENO}` shows literally | Token not supported in body (only in headers/footers) | Move to `<htmlpagefooter>` |
+| Hindi/Unicode text missing | Wrong font set | Use `freeserif` or `dejavusans`; enable `autoScriptToLang` |
+| Image not loading | Relative path | Use absolute server path or `{{H_logo_abs}}` token |
+| Page size wrong | Using `size:` in @page | Use `format` in Mpdf constructor instead |
+| Margins not applied | `@page` CSS absent or conflicting constructor values | When using `@page` CSS, constructor margins act as fallback only |
+
+---
+
+## 12. References
+
+- Full docs: https://mpdf.github.io/
+- Named HTML headers (Method 4): https://mpdf.github.io/headers-footers/method-4.html
+- Supported CSS: https://mpdf.github.io/css-stylesheets/supported-css.html
+- @page CSS: https://mpdf.github.io/paging/using-page.html
+- Fonts in mPDF 7+: https://mpdf.github.io/fonts-languages/fonts-in-mpdf-7-x.html
+- WriteHTML: https://mpdf.github.io/reference/mpdf-functions/writehtml.html