Command-line No valid ImageMagick found

In some cases, the ImageMagick command-line binary is not found. Even if ImageMagic exist.
The problem occurs in this function: function_exists('shell_exec') returns an empty result when using $whereIsCommand $fullpath. As a workaround, I had to comment out that check and instead use @is_executable($fullpath).”

function ime_is_executable($fullpath) {
	$whereIsCommand = (PHP_OS == 'WINNT') ? 'where' : 'which';
	return function_exists('shell_exec') ? $whereIsCommand $fullpath : @is_executable($fullpath);
}

function ime_is_executable($fullpath) {
	$whereIsCommand = (PHP_OS == 'WINNT') ? 'where' : 'which';
	return @is_executable($fullpath);
}