Php – How to Set Variables in a Laravel Blade Template

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I'm reading the Laravel Blade documentation and I can't figure out how to assign variables inside a template for use later. I can't do {{ $old_section = "whatever" }} because that will echo "whatever" and I don't want that.

I understand that I can do <?php $old_section = "whatever"; ?>, but that's not elegant.

Is there a better, elegant way to do that in a Blade template?

Best Answer

LARAVEL 5.5 AND UP

Use the full form of the blade directive:

@php
$i = 1
@endphp

LARAVEL 5.2 - 5.4

You can use the inline tags:

@php ($i = 1)

Or you can use it in a block statement:

@php
$i = 1
@endphp

ADD A 'DEFINE' TAG

If you want to use custom tags and use a @define instead of @php, extend Blade like this:

/*
|--------------------------------------------------------------------------
| Extend blade so we can define a variable
| <code>
| @define $variable = "whatever"
| </code>
|--------------------------------------------------------------------------
*/

\Blade::extend(function($value) {
    return preg_replace('/\@define(.+)/', '<?php ${1}; ?>', $value);
});

Then do one of the following:

Quick solution: If you are lazy, just put the code in the boot() function of the AppServiceProvider.php.

Nicer solution: Create an own service provider. See https://stackoverflow.com/a/28641054/2169147 on how to extend blade in Laravel 5. It's a bit more work this way, but a good exercise on how to use Providers :)

LARAVEL 4

You can just put the above code on the bottom of app/start/global.php (or any other place if you feel that is better).

After the above changes, you can use:

@define $i = 1

to define a variable.

Related Solutions

Php – Enumerations on PHP

Depending upon use case, I would normally use something simple like the following:

abstract class DaysOfWeek
{
    const Sunday = 0;
    const Monday = 1;
    // etc.
}

$today = DaysOfWeek::Sunday;

However, other use cases may require more validation of constants and values. Based on the comments below about reflection, and a few other notes, here's an expanded example which may better serve a much wider range of cases:

abstract class BasicEnum {
    private static $constCacheArray = NULL;

    private static function getConstants() {
        if (self::$constCacheArray == NULL) {
            self::$constCacheArray = [];
        }
        $calledClass = get_called_class();
        if (!array_key_exists($calledClass, self::$constCacheArray)) {
            $reflect = new ReflectionClass($calledClass);
            self::$constCacheArray[$calledClass] = $reflect->getConstants();
        }
        return self::$constCacheArray[$calledClass];
    }

    public static function isValidName($name, $strict = false) {
        $constants = self::getConstants();

        if ($strict) {
            return array_key_exists($name, $constants);
        }

        $keys = array_map('strtolower', array_keys($constants));
        return in_array(strtolower($name), $keys);
    }

    public static function isValidValue($value, $strict = true) {
        $values = array_values(self::getConstants());
        return in_array($value, $values, $strict);
    }
}

By creating a simple enum class that extends BasicEnum, you now have the ability to use methods thusly for simple input validation:

abstract class DaysOfWeek extends BasicEnum {
    const Sunday = 0;
    const Monday = 1;
    const Tuesday = 2;
    const Wednesday = 3;
    const Thursday = 4;
    const Friday = 5;
    const Saturday = 6;
}

DaysOfWeek::isValidName('Humpday');                  // false
DaysOfWeek::isValidName('Monday');                   // true
DaysOfWeek::isValidName('monday');                   // true
DaysOfWeek::isValidName('monday', $strict = true);   // false
DaysOfWeek::isValidName(0);                          // false

DaysOfWeek::isValidValue(0);                         // true
DaysOfWeek::isValidValue(5);                         // true
DaysOfWeek::isValidValue(7);                         // false
DaysOfWeek::isValidValue('Friday');                  // false

As a side note, any time I use reflection at least once on a static/const class where the data won't change (such as in an enum), I cache the results of those reflection calls, since using fresh reflection objects each time will eventually have a noticeable performance impact (Stored in an assocciative array for multiple enums).

Now that most people have finally upgraded to at least 5.3, and SplEnum is available, that is certainly a viable option as well--as long as you don't mind the traditionally unintuitive notion of having actual enum instantiations throughout your codebase. In the above example, BasicEnum and DaysOfWeek cannot be instantiated at all, nor should they be.

Php – How to get useful error messages in PHP

For syntax errors, you need to enable error display in the php.ini. By default these are turned off because you don't want a "customer" seeing the error messages. Check this page in the PHP documentation for information on the 2 directives: error_reporting and display_errors. display_errors is probably the one you want to change. If you can't modify the php.ini, you can also add the following lines to an .htaccess file:

php_flag  display_errors        on
php_value error_reporting       2039

You may want to consider using the value of E_ALL (as mentioned by Gumbo) for your version of PHP for error_reporting to get all of the errors. more info

3 other items: (1) You can check the error log file as it will have all of the errors (unless logging has been disabled). (2) Adding the following 2 lines will help you debug errors that are not syntax errors:

error_reporting(-1);
ini_set('display_errors', 'On');

(3) Another option is to use an editor that checks for errors when you type, such as PhpEd. PhpEd also comes with a debugger which can provide more detailed information. (The PhpEd debugger is very similar to xdebug and integrates directly into the editor so you use 1 program to do everything.)

Cartman's link is also very good: http://www.ibm.com/developerworks/library/os-debug/

Best Answer

Related Solutions

Php – Enumerations on PHP

Php – How to get useful error messages in PHP

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