Show what error levels are included in a given error_reporting() value

error_levels.php

<?php

if( $_SERVER['argc'] === 1 ) {
        printf(
                'No error level specified as argument (%s <errorlevel>), using current error_reporting value...' . PHP_EOL
                , $_SERVER['argv'][0]
        );

        $errorlevel = error_reporting();
} else {
        $errorlevel = (int) $_SERVER['argv'][1];
}

$constants = get_defined_constants(true);

// add some custom error constants
$constants['Core']['E_ALL | E_STRICT'] = E_ALL | E_STRICT;

foreach( $constants['Core'] as $name => $value ) {
        if( strpos($name , 'E_' ) === 0 ) {
                if( ( $errorlevel & $value ) === $value ) {
                        printf( '%5d → %s' . PHP_EOL , $value , $name );
                }
        }
}

//printf( '%5d → E_ALL | E_STRICT' . PHP_EOL , E_ALL | E_STRICT );

printf( '-------------------------------' . PHP_EOL );
printf( '%5d → current error level' . PHP_EOL , $errorlevel );