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---
layout: default
title: Inline Parsing
description: Parsing inline elements with a custom parser
---
# Inline Parsing
There are two ways to implement custom inline syntax:
- Inline Parsers (covered here)
- [Delimiter Processors](/1.6/customization/delimiter-processing/)
The difference between normal inlines and delimiter-run-based inlines is subtle but important to understand. In a nutshell, delimiter-run-based inlines:
- Are denoted by "wrapping" text with one or more characters before **and** after those inner contents
- Can contain other delimiter runs or inlines inside of them
An example of this would be emphasis:
```markdown
This is an example of **emphasis**. Note how the text is *wrapped* with the same character(s) before and after.
```
If your syntax looks like that, consider using a [delimiter processor](/1.6/customization/delimiter-processing/) instead. Otherwise, an inline parser is your best bet.
## Implementing Inline Parsers
Inline parsers should implement `InlineParserInterface` and the following two methods:
### getCharacters()
This method should return an array of single characters which the inline parser engine should stop on. When it does find a match in the current line the `parse()` method below may be called.
### parse()
This method will be called if both conditions are met:
1. The engine has stopped at a matching character; and,
2. No other inline parsers have successfully parsed the character
#### Parameters
- `InlineParserContext $inlineContext` - Encapsulates the current state of the inline parser, including the [`Cursor`](/1.6/customization/cursor/) used to parse the current line.
#### Return value
`parse()` should return `false` if it's unable to handle the current line/character for any reason. (The [`Cursor`](/1.6/customization/cursor/) state should be restored before returning false if modified). Other parsers will then have a chance to try parsing the line. If all registered parsers return false, the character will be added as plain text.
Returning `true` tells the engine that you've successfully parsed the character (and related ones after it). It is your responsibility to:
1. Advance the cursor to the end of the parsed text
2. Add the parsed inline to the container (`$inlineContext->getContainer()->appendChild(...)`)
## Inline Parser Examples
### Example 1 - Twitter Handles
Let's say you wanted to autolink Twitter handles without using the link syntax. This could be accomplished by registering a new inline parser to handle the `@` character:
```php
use League\CommonMark\Environment;
use League\CommonMark\Inline\Element\Link;
use League\CommonMark\Inline\Parser\InlineParserInterface;
use League\CommonMark\InlineParserContext;
class TwitterHandleParser implements InlineParserInterface
{
public function getCharacters(): array
{
return ['@'];
}
public function parse(InlineParserContext $inlineContext): bool
{
$cursor = $inlineContext->getCursor();
// The @ symbol must not have any other characters immediately prior
$previousChar = $cursor->peek(-1);
if ($previousChar !== null && $previousChar !== ' ') {
// peek() doesn't modify the cursor, so no need to restore state first
return false;
}
// Save the cursor state in case we need to rewind and bail
$previousState = $cursor->saveState();
// Advance past the @ symbol to keep parsing simpler
$cursor->advance();
// Parse the handle
$handle = $cursor->match('/^[A-Za-z0-9_]{1,15}(?!\w)/');
if (empty($handle)) {
// Regex failed to match; this isn't a valid Twitter handle
$cursor->restoreState($previousState);
return false;
}
$profileUrl = 'https://twitter.com/' . $handle;
$inlineContext->getContainer()->appendChild(new Link($profileUrl, '@' . $handle));
return true;
}
}
$environment = Environment::createCommonMarkEnvironment();
$environment->addInlineParser(new TwitterHandleParser());
```
### Example 2 - Emoticons
Let's say you want to automatically convert smilies (or "frownies") to emoticon images. This is incredibly easy with an inline parser:
```php
use League\CommonMark\Environment;
use League\CommonMark\Inline\Element\Image;
use League\CommonMark\Inline\Parser\InlineParserInterface;
use League\CommonMark\InlineParserContext;
class SmilieParser implements InlineParserInterface
{
public function getCharacters(): array
{
return [':'];
}
public function parse(InlineParserContext $inlineContext): bool
{
$cursor = $inlineContext->getCursor();
// The next character must be a paren; if not, then bail
// We use peek() to quickly check without affecting the cursor
$nextChar = $cursor->peek();
if ($nextChar !== '(' && $nextChar !== ')') {
return false;
}
// Advance the cursor past the 2 matched chars since we're able to parse them successfully
$cursor->advanceBy(2);
// Add the corresponding image
if ($nextChar === ')') {
$inlineContext->getContainer()->appendChild(new Image('/img/happy.png'));
} elseif ($nextChar === '(') {
$inlineContext->getContainer()->appendChild(new Image('/img/sad.png'));
}
return true;
}
}
$environment = Environment::createCommonMarkEnvironment();
$environment->addInlineParser(new SmilieParserParser());
```
## Tips
- For best performance, `return false` **as soon as possible**.
- You can `peek()` without modifying the cursor state. This makes it useful for validating nearby characters as it's quick and you can bail without needed to restore state.
- You can look at (and modify) any part of the AST if needed (via `$inlineContext->getContainer()`).
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