slots.md

Slots

Slots are the core processing units of Templex. Each slot handles a specific type of template directive, performing replacement and hydration to produce the final rendered output.

Default Slots

Templex includes four built-in slots, processed in this order:

1. IncludeSlot — includes another template's content
2. ControlSlot — processes control flow (if/else, foreach, for, switch)
3. TernarySlot — resolves ternary and null coalescing expressions
4. VariableSlot — replaces variable placeholders

Custom Slots

You can extend Templex with custom slots that implement SlotInterface:

$templex->setSlots([
    CustomSlot::class,
    IncludeSlot::class,
    ControlSlot::class,
    VariableSlot::class,
]);

---

Includes

Include another template by its name to create reusable partials:

<{ include partials.header }>
<{ include layouts.base }>

Dot notation maps to subdirectories, so partials.header resolves to partials/header.stub.

---

Variables

Variables are replaced when matching placeholders are found. They can be passed in at render time, or created by other slots such as loops.

Hello <{ $name }>, welcome to <{ $siteName }>!

$templex->render('greeting', [
    'name'     => 'Fred',
    'siteName' => 'Templex',
]);

---

Conditions

If/else statements support variables, numbers, booleans, and literal strings with the usual comparison operators.

<{ if( $role === 'admin' ) }>
    <p>Welcome, administrator.</p>
<{ endif }>

With an else branch:

<{ if( $authenticated ) }>
    <p>You are logged in.</p>
<{ else }>
    <p>Please log in.</p>
<{ endif }>

With elseif for chained conditions:

<{ if( $role === "admin" ) }>
    <p>Administrator</p>
<{ elseif( $role === "editor" ) }>
    <p>Editor</p>
<{ else }>
    <p>Guest</p>
<{ endif }>

Multiple elseif branches are supported — the first matching condition wins.

Supported Operators

==, ===, !=, !==, >, <, >=, <=, &&, ||, !

Self-Evaluation

A variable on its own evaluates as truthy or falsy:

<{ if( $hasAccess ) }>
    Granted
<{ endif }>

Boolean Literals

<{ if( true ) }>
    Always shown
<{ endif }>

Logical Operators

Combine conditions with && (and) and || (or):

<{ if( $isLoggedIn && $isAdmin ) }>
    Admin panel
<{ endif }>

<{ if( $role === "admin" || $role === "editor" ) }>
    Can edit
<{ endif }>

Negation

Negate any condition with !:

<{ if( !$banned ) }>
    Welcome
<{ endif }>

Conditions can be nested and combined with other control structures. For more examples including nested conditions, logical operators, and operator usage, see the Condition Examples.

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Foreach Loops

Foreach loops iterate over an array variable:

<ul>
    <{ foreach( $users as $user ) }>
        <li><{ $user }></li>
    <{ endforeach }>
</ul>

Key-value iteration is also supported using $key => $value syntax:

<dl>
    <{ foreach( $settings as $key => $value ) }>
        <dt><{ $key }></dt>
        <dd><{ $value }></dd>
    <{ endforeach }>
</dl>

The loop variables are scoped to the loop body and have access to all parent variables. Loop metadata variables ($loop_index, $loop_first, $loop_last, $loop_count) are also available. For more examples including nested loops and key-value patterns, see the Foreach Examples.

---

For Loops

For loops use C-style syntax with initialization, condition, and increment:

<{ for( $i = 0; $i < 5; $i++ ) }>
    Item <{ $i }>
<{ endfor }>

Variables can be used for dynamic bounds:

<{ for( $i = $start; $i <= $end; $i++ ) }>
    Value: <{ $i }>
<{ endfor }>

Supported Increments

• $i++ / $i--
• $i += 2 / $i -= 1

Supported Condition Operators

<, <=, >, >=, ==, ===, !=, !==

For more examples including nested loops, tables, and pagination patterns, see the For Loop Examples.

Why no while loop? Templex variables are immutable within a template, so a while loop condition can never change between iterations. Use for loops with a counter or foreach loops over a collection instead.

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Loop Metadata

Both foreach and for loops expose metadata variables inside the loop body:

Variable	Description
$loop_index	Zero-based iteration index (0, 1, 2, ...)
$loop_count	Total number of iterations
$loop_first	true on the first iteration
$loop_last	true on the last iteration

<{ foreach( $items as $item ) }>
    <{ if( $loop_first ) }>First: <{ endif }><{ $item }>
    <{ if( $loop_last ) }> (last of <{ $loop_count }>)<{ endif }>
<{ endforeach }>

These work identically in for loops:

<{ for( $i = 0; $i < 5; $i++ ) }>
    <{ $loop_index }>: <{ $i }><{ if( $loop_last ) }> [done]<{ endif }>
<{ endfor }>

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Switch Statements

Switch statements match a variable against multiple cases:

<{ switch( $status ) }>
    <{ case( "active" ) }>
        Account is active
    <{ case( "suspended" ) }>
        Account is suspended
    <{ default }>
        Unknown status
<{ endswitch }>

Cases support strings, numbers, booleans, and variables. Matching uses strict comparison (===). There is no fallthrough — each case is independent.

<{ switch( $level ) }>
    <{ case( 1 ) }>
        Beginner
    <{ case( $maxLevel ) }>
        Expert
    <{ default }>
        Intermediate
<{ endswitch }>

For more examples including nested switches and variable cases, see the Switch Statement Examples.

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Ternary and Null Coalescing

Inline expressions for simple conditional output without full if/else blocks.

Ternary

Output different values based on a variable's truthiness:

<{ $active ? "Enabled" : "Disabled" }>
<{ $count ? "Has items" : "Empty" }>

Truthy: true, 1, non-empty strings (except "false" and "0"). Falsy: false, 0, "", "false", "0", or missing variables.

Null Coalescing

Provide a default value when a variable doesn't exist:

<{ $title ?? "Untitled" }>
<{ $theme ?? "light" }>

If the variable exists, its value is used. If it doesn't exist, the default is used.

Values

Both ternary and null coalescing support string literals, numbers, and variable references:

<{ $name ?? $defaultName }>
<{ $role ? $adminLabel : $guestLabel }>
<{ $port ?? 8080 }>

Ternary and null coalescing work inside loops and other control structures.