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Pars'Em Template Engine

Pars'Em logo

Simple lightweight templating engine made in PHP.

Enhance your files with variables, conditional blocks and PHP functions as filters. Create re-usable templates by adding variable <% placeholder %>'s anywhere in your file and have the content change dynamically based on the arguments you provide.

Features

  • Parse string templates to string
    • Replace variable placeholders with provided arguments
    • Apply filter functions to variables
    • Use <% if %> blocks to conditionally parse the template
      • Use <% else %> blocks to provide an alternative content if the condition is not met
  • Parse template files to string
    • Parse the entire file as a string
  • Provide a custom regex pattern to parse functions to use a custom syntax
  • Get all variables from a template

Requirements

  • PHP >= 8.2
  • Composer

Installation

Install with Composer:

composer require matronator/parsem

And then just add the dependency to your PHP file/s:

use Matronator\Parsem\Parser;

Templates Syntax Highlighting for VS Code

To get syntax highlighting for template files (highlight <% variable|placeholders %> and <% if %><% else %><% endif %> even inside strings), you can download the MTRGen Templates Syntax Highlighting extension for VS Code.

Usage

Template syntax

Conditions

You can use conditions in your templates by using the <% if %> and <% endif %> tags. The condition must be a valid PHP expression that will be evaluated and if it returns true, the content between the tags will be included in the final output.

You can also use the <% else %> tag to provide an alternative content if the condition is not met.

To use a variable provided in the arguments array in a condition, you must use the $ sign before the variable name, like this: <% if $variable == 'value' %>. The $ sign is used to differentiate between the template variable and a keyword such as true or null.

Example:
some:
  key
  <% if $variable == 'value' %>
  with value
  <% else %>
  without value
  <% endif %>

If you provide an argument ['variable' => 'value'], the final output will be this:

some:
  key
  with value

And if you provide an argument ['variable' => 'other value'], the final output will be this:

some:
  key
  without value

Variables

Variables are wrapped in <% and %> with optional space on either side (both <%nospace%> and <% space %> are valid) and the name must be an alphanumeric string with optional underscore/s (this regex [a-zA-Z0-9_]+?).

Default values

Variables can optionally have a default value that will be used if no argument is provided for that variable during parsing. You can specify a default value like this: <% variable='Default' %>

If you're going to use filters, the default value comes before the filter, ie.: <% variable='Default'|filter %>

If default value is empty (ie. <% var= %>), it will be treated as null.

Filters

You can optionally provide filter to a variable by placing the pipe symbol | right after the variable name and the filter right after that (no space around the | pipe symbol), like this: <% variable|filter %>.

The filter can be any PHP function with the variable used as the function's argument.

Example:

If we have <% foo|strtoupper %> in the template and we provide an argument ['foo' => 'hello world'], the final (parsed) output will be this: HELLO WORLD.

Filters can also have additional arguments apart from the variable itself. To pass additional arguments to a filter, write it like this: <% var|filter:'arg','arg2',20,true %>. Each argument after the colon is separated by a comma and can have any scalar type as a value.

The first argument will always the variable on which we're declaring the filter, with any other arguments passed after that.

Example:

If we have <% foo|substr:1,3 %> and provide an argument ['foo' => 'abcdef'], the filter will get called like this using the arguments provided: substr('abcdef', 1, 3). And the final parsed output will thus be this: bcd.

So far you can specify only one filter per variable declaration, but that will probably change in the future.

Built-in filters

There are a few built-in filters that you can use:

upper - Converts the variable to uppercase

lower - Converts the variable to lowercase

upperFirst - Converts the first character of the variable to uppercase

lowerFirst - Converts the first character of the variable to lowercase

first - Returns the first character of the variable

last - Returns the last character of the variable

camelCase - Converts the variable to camelCase

snakeCase - Converts the variable to snake_case

kebabCase - Converts the variable to kebab-case

pascalCase - Converts the variable to PascalCase

titleCase - Converts the variable to Title Case

length - Returns the length of the variable

reverse - Reverses the variable

random - Returns a random character from the variable

truncate - Truncates the variable to the specified length

Use in code

Parse string or file

There are two main functions that will be of most interest to you: parseString and parse. Both are static functions and are used like this:

use Matronator\Parsem\Parser;

// parseString()
echo Parser::parseString('some <%text%>.', ['text' => 'value']);
// Output: some value.

// parse()
$arguments = [
    'variableName' => 'value',
    'key' => 'other value',
];
$parsedFile = Parser::parse('filename.yaml', $arguments);
echo $parsedFile;
// Output: Will print the parsed contents of the file as string.

Methods

Parser::parseString
/**
 * Parses a string, replacing all template variables with the corresponding values passed in `$arguments`.
 * @return mixed The parsed string or the original `$string` value if it's not string
 * @param mixed $string String to parse. If not provided with a string, the function will return this value
 * @param array $arguments Array of arguments to find and replace while parsing `['key' => 'value']`
 * @param bool $strict [optional] If set to `true`, the function will throw an exception if a variable is not found in the `$arguments` array. If set to `false` null will be used.
 * @param string|null $pattern [optional] You can provide custom regex with two matching groups (for the variable name and for the filter) to use custom template syntax instead of the default one `<% name|filter %>`
 * @throws RuntimeException If a variable is not found in the `$arguments` array and `$strict` is set to `true`
 */
Parser::parseString(mixed $string, array $arguments = [], bool $strict = true, ?string $pattern = null): mixed
Parser::parse
/**
 * @param string $filename Path to the file to parse
 * @see Parser::parseString() for rest of the parameter descriptions
 */
Parser::parse(string $filename, array $arguments = [], bool $strict = true, ?string $pattern = null): string