Check if variable exist in laravel's blade directive - php

Question

I'm trying to create blade directive which echo variable (if variable defined) or echo "no data" if variable undefined.
This is my code in AppServiceProvider.php:
<?php
namespace App\Providers;
use Blade;
use Illuminate\Support\ServiceProvider;
class AppServiceProvider extends ServiceProvider
{
/**
* Bootstrap any application services.
*
* #return void
*/
public function boot()
{
Blade::directive('p', function($ex) {
error_log(print_r($ex,true));
return '<?php $defined_vars = get_defined_vars(); if(array_key_exists(\''. $ex .'\', $defined_vars) ): echo ' . $ex . ' ; else: echo \'no data\'; endif;?>';
});
}
/**
* Register any application services.
*
* #return void
*/
public function register()
{
//
}
}
Here is my index.blade.php:
<p class="lead">#p($myvar)</p>
But my directive "p" gives "no data" if variable defined.
If I use isset error occurres: Cannot use isset() on the result of an expression (you can use "null !== expression" instead)
How could I check inside directives if variable defined?

Answer 1

Blade has a directive to check if a variable is set:
#isset($var)
#endisset

Answer 2

Try checking if the variable is empty:
#if(empty($myvar))
<p>Data does not exist</p>
#else
<p>Your data is here!</p>
#endif
Can also check this thread

Answer 3

For Laravel 5.7 onwards use.
{{ $checkvariable ?? 'not-exist' }}

Answer 4

You can use in Blade functionality for checking isset i.e
{{ $checkvariable or 'not-exist' }}
https://laravel.com/docs/5.2/blade#displaying-data

Answer 5

For Laravel version >=5.7
{{ $value ?? '' }}
For Laravel version <5.7
{{ $value or '' }}

Answer 6

The best and cleanest way check if a variable exists in blade:
{!! !empty($myvariable) ? $myvariable : 'variable does not exist' !!}

Answer 7

You can use the #isset blade directive to check whether the variable is set or not. Alternatively, if you have the default value for that variable you can directly use it as {{ $vatiable ?? 'default_value' }}. The ?? way is available in Laravel v5.7 onwards.
If you want to check for multiple variables at once, you can do it by applying AND operation to expression as #if(isset($var_one) && isset($var_two)).
There are also other ways (lengthy) using #if directive as #if(isset($variable)) but it's not recommended.
Some developer uses # symbol for error control in a similar situation. The at-sign (#) is used as error control operator in PHP. When an expression is prepended with the # sign, error messages that might be generated by that expression will be ignored. If the track_errors feature is enabled, an error message generated by the expression and it will be saved in the variable $php_errormsg. This variable will be overwritten on each error. The use of # is very bad programming practice as it does not make the error disappear, it just hides them, and it makes debugging a lot worse since we can’t see what’s actually wrong with our code.

Answer 8

You can do it in few different ways.
Sample-1:
#if( !empty($data['var']))
{{ $data['var'] }}
#endif
Sample-2:
{{ $data['var'] or 'no data found' }}
Sample-3: Using ternary operator
<a href="" class="{{ ( ! empty($data['var'] ? $data['var'] : 'no data found') }}">

Answer 9

For the last version of Larvael make the variable optional in the blade template.
Replace $myvar with
{{ $myvar }} with {{ $myvar?? '' }}

Answer 10

What are you trying to pass to your custom directive? If it's just a string/int the following should work.
Blade::directive('p', function($expression){
$output = $expression ? $expression : 'nodata';
return "<?php echo {$output}; ?>";
});
In Blade Template
#p('Foo')

Answer 11

The #empty directive might be useful:
#empty($var)
$var is unset or false-y
#endempty

Answer 12

To check if variable exist in Laravel blade directive, do this:
Blade::directive('datetime', function ($value) {
return "<?php echo isset($value) ? ($value)->format('d/m/Y H:i:s') : null; ?>";
});

Answer 13

If you trying check a bool variable you can use #unless
<input type="text" class="#unless ($variable) d-none #endunless" >